Hunt on behalf of time (6)
I believe the answer is:
forage
'hunt' is the definition.
(I know that forage is a type of hunt)
'on behalf of time' is the wordplay.
'on behalf of' becomes 'for' (eg speaking on behalf of or for someone else).
'time' becomes 'age' (an age is a period of time).
'for'+'age'='FORAGE'
(Other definitions for forage that I've seen before include "Rummage, search for" , "Go searching, perhaps for food" , "Rummage, go searching" , "Search widely for food" , "Hunt for food or provisions" .)