Puzzles, seeing large cup in nettles (7)
I believe the answer is:
riddles
'puzzles' is the definition.
(riddling is a kind of puzzling)
'large cup in nettles' is the wordplay.
'large cup' becomes 'DD' (DD is a bra cup size).
'in' means one lot of letters goes inside another.
'nettles' becomes 'riles' ('rile' can be a synonym of 'nettle').
'dd' placed within 'riles' is 'RIDDLES'.
'seeing' is the link.
(Other definitions for riddles that I've seen before include "Conundrums" , "Tricky questions" , "Coarse sieves or puzzles" , "Funny little teasers" , "Questions designed to test ingenuity" .)