Nipper's apple? (4)
I believe the answer is:
crab
I believe this is a double definition.
'nipper's' is the first definition.
(I have seen 'Nautical nipper' mean 'crab' so perhaps 'nipper' could also mean 'crab')
'apple?' is the second definition.
(crab apple is a kind of apple)
(Other definitions for crab that I've seen before include "One may be caught" , "Food from the sea" , "Sour character" , "Shellfish with pincers" , "Seafood (that can be caught by a rower?)" .)