Equalled chat about sea outside (7)
I believe the answer is:
matched
'equalled' is the definition.
('match' can be a synonym of 'equal')
'chat about sea outside' is the wordplay.
'about' is an anagram indicator.
'sea' becomes 'med' (short for Mediterranean).
'outside' indicates putting letters inside (some letters go outside others).
'chat' is an anagram of 'atch'.
'atch' placed within 'med' is 'MATCHED'.
(Other definitions for matched that I've seen before include "Equalled; paired" , "Equalised" , "having opposition" , "Put like with like" , "Exactly alike" .)