War zone aid, one with companion picking up litter? (9,6)

'war zone aid' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.

'one with companion picking up litter?' is the wordplay.
I cannot quite see how this works, but
'one' could be 'a' and 'a' is present in the answer.
'companion' could be 'ch' (I've seen this in other clues) and 'ch' is found in the answer.
'litter?' could be 'be' (littering is a kind of being) and 'be' is present in the answer.
This explanation may well be incorrect...