Independent, boring, average couple (4)
I believe the answer is:
pair
'couple' is the definition.
('pair' can be a synonym of 'couple')
'independent boring average' is the wordplay.
'independent' becomes 'i'.
'boring' means one lot of letters goes inside another (some letters must 'bore' a hole into other letters).
'average' becomes 'par' (I've seen this before).
'i' put within 'par' is 'PAIR'.
(Other definitions for pair that I've seen before include "Brace, couple" , "item" , "E.g. two aces; mate" , "Twosome" , "Husband and wife" .)