Choose a chap something sour (7)
I believe the answer is:
pickles
'something sour' is the definition.
I can't judge whether this definition defines the answer.
'choose a chap' is the wordplay.
'choose' becomes 'pick' (picking is a kind of choosing).
'a chap' becomes 'les' ().
'pick'+'les'='PICKLES'
Can you help me to learn more?
(Other definitions for pickles that I've seen before include "Preserves in vinegar or brine" , "Vegetables preserved in vinegar or brine" .)