Using force in street unacceptably after wife leaves (8)
I believe the answer is:
strongly
'using force' is the definition.
(done with force or strength)
'street unacceptably after wife leaves' is the wordplay.
I cannot really see how this works, but
'street' could be 'st' (abbreviation) and 'st' is found in the answer.
This explanation may well be incorrect...
'in' is the link.
Can you help me to learn more?
(Other definitions for strongly that I've seen before include "Firmly or with great power" , "With power or strength" , "In a forceful manner" , "hard" , "In a powerful manner" .)