The clues:
Each of the clues makes a reference to Level (even, tier, etc.), 51 (usually in Roman, LI) or Level 51 (I, me, occasionally L + LI). I've only added brief explanations below. (XXX< means reversal, XXX* means anagram, {xxx} means omission.)
Getting 51 and nice guy to start (7)
— LANDING, L AND I + N{ice} + G{uy}
Level 51 not this (4)
— EVEN, cryptical: 51 is odd
Totems you shouldn't have—51's being cautious, ultimately (9)
— TALISMANS, TA (you shouldn't have) + LI'S + MAN + S
Level 51 with way to create viability ranking (4, 4)
— TIER LIST, TIER + LI (51) + ST(reet)
Losing heart, Level extremely lost, taking magazines to top (7)
— ECLIPSE, CLIPS in {l}E{v}E{l}
Level rolls in wine, perhaps drunk? (8)
— REVELLED, LEVEL* in RED
Thought derailed: i.e. bid Level 51 gone (8)
— BELIEVED, (IE + B{I}D + LEVE{L})*
Team of Level, even in part? (6)
— ELEVEN, hidden in {lev}EL EVEN
Alien with straw takes Level 51 to the Empire State Building? (7)
— H • • • • • •
Upset Level 51: old girl informally overshadowed in-charge—ridiculous! (9)
— ILLOGICAL, (L + LI)< + IC in (O + GAL)
Those like 51 narcotics, maybe? (7)
— NUMBERS, cryptical: narcotics numb
Level 51 mum after trial (8)
— DEMOLISH, DEMO + LI + SH
Level 51 yearned, initially, to hold more detailed tribute (6)
— MEMORY, MOR{e} in (ME + Y{earned})
Initially year-end, Level loses the night before, finally snaps and shouts (5)
— YELLS, Y{ear} E{nd} + L{eve}L + {snap}S
Character, approximately Level 51, eating electro-optics and cell parts (8)
— NUCLEOLI, EO inside (NU + L + LI)
Level 51 venturing into silver cave in turn (7)
— ALIGNED, LI in AG + DEN<
Chunk of meat from Level 51 eaten by crazy daemon? (9)
— MEDALLION, L + LI in DAEMON*
Level 51 looking back and beheading one who cries for rock (7)
— EMERALD, ME< + {h}ERALD
The answer:
Taking the first letters from each clue yields:
Letter behind my name
When I posted the answers to the clue last night, I didn't know what to do with it. Fortunately, SteveV was so good to put me out of my misery: Take the letter after the poster's name in each clue and you get:
Answer: Get on my level
Which, of course, answers the question in the preamble: The answer to this puzzle is what you should do to solve this puzzle. Speaking of self-referential humour ... :)
Thanks to Level 51 for a very good puzzle and to SteveV for bringing me on the final level.