Betray trust, holding current allowance (6)
I believe the answer is:
ration
'allowance' is the definition.
(I've seen this before)
'betray trust holding current' is the wordplay.
'betray trust' becomes 'rat on' (to rat on someone is to betray them).
'holding' is an insertion indicator.
'current' becomes 'I' (symbol for electric current).
'raton' placed around 'i' is 'RATION'.
(Other definitions for ration that I've seen before include "Limited allocation of food etc in wartime" , "Dole out in measured quantities, as in time of shortage" , "A fixed allowance in times of scarcity" , "Share or allotment, of food say" , "Apportion" .)