Absolutely having to match (7)
I believe the answer is:
totally
'absolutely' is the definition.
('totally' can be a synonym of 'absolutely')
'to match' is the wordplay.
'match' becomes 'tally' ('tally' can be a synonym of 'match').
'to'+'tally'='TOTALLY'
'having' acts as a link.
(Other definitions for totally that I've seen before include "Fully, completely" , "in every respect" , "Completely, entirely" , "Clean" , "to the nth degree" .)