Fighting when picking up uncooked food (7)
I believe the answer is:
warfare
'fighting' is the definition.
(fighting a war)
'picking up uncooked food' is the wordplay.
'picking up' says the letters should be written in reverse (in a down clue, letters go up).
'uncooked' becomes 'raw' (similar in meaning).
'food' becomes 'fare' (fare is a kind of food).
'raw' reversed gives 'war'.
'war'+'fare'='WARFARE'
'when' is the link.
(Other definitions for warfare that I've seen before include "Combat" , "Struggle" , "Strife" , "All-out fighting" , "action" .)