Swears at cricket matches (7)
I believe the answer is:
attests
'swears' is the definition.
(attesting is a kind of swearing)
'at cricket matches' is the wordplay.
'cricket matches' becomes 'tests' (I've seen this in other clues).
'at'+'tests'='ATTESTS'
(Other definitions for attests that I've seen before include "Confirms" , "Certifies" , "Sat test (anag.)" , "Authenticates or affirms to be true" , "Gives evidence in court" .)