Vague amount (3)
I believe the answer is:
any
'vague amount' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for any that I've seen before include "Some; none in particular" , "One or some, whichever you choose" , "A lot < ? Not a lot < -- some" , "Several" , "'Whatever'" .)