A fifth of money put in collection so far (2,3)
I believe the answer is:
as yet
'so far' is the definition.
(I've seen this before)
'a fifth of money put in collection' is the wordplay.
'fifth of money' becomes 'y' (5th letter of 'money').
'put in' indicates putting letters inside.
'collection' becomes 'set' (set is a kind of collection).
'y' put within 'set' is 'syet'.
'a'+'syet'='AS YET'
(Other definitions for as yet that I've seen before include "Thus far" , "Up to this point in time" , "Up till now" .)