My infix is a potato reporter,
My suffix is a garden storer,
My prefix is Martin's significant other,
My whole will make you bowled over.
What am I?
The answer is:
ASTONISHED
My infix is a potato reporter,
This clues NISH Kumar - a British stand-up comedian who hosts the BBC Two show The Mash Report. With the connection between 'mash' and 'potato', Nish could be considered a 'potato reporter'.
Original attempt, superseded: I sounds like 'EYE', a growing point on the skin of a potato. 'Reporter' here is intended as a 'sounds like' indicator like in a cryptic crossword clue...
My suffix is a garden storer,
A SHED is a building used for storage found in a garden.
My prefix is Martin's significant other,
ASTON Martin is a British car manufacturer, famously favoured by the fictional secret agent James Bond.
My whole will make you bowled over.
ASTON + NISH + SHED = ASTONISHED is a synonym for 'bowled over' or 'surprised' (as in the title).