He picks pickles when hungry (7)
I believe the answer is:
peckish
'hungry' is the definition.
(similar in meaning)
'he picks pickles' is the wordplay.
'pickles' indicates anagramming the letters (I've seen 'pickled' mean this (I've seen this in other clues)).
'he'+'picks'='hepicks'
'hepicks' is an anagram of 'PECKISH'.
'when' acts as a link.
(Other definitions for peckish that I've seen before include "Wanting something to eat" , "Getting hungry (informal)" , "ready for dinner?" , "Feeling slightly hungry" , "Informally hungry - like a bird?" .)