Extremely nice, after work, I suppose (5)
I believe the answer is:
opine
'suppose' is the definition.
(thesaurus)
'extremely nice after work i' is the wordplay.
'extremely' says to hollow out the word (remove centre letters).
'after' says to put letters next to each other.
'work' becomes 'op' (abbreviation for opus**).
'nice' with its centre taken out is 'ne'.
'op'+'i'='opi'
'ne' after 'opi' is 'OPINE'.
(Other definitions for opine that I've seen before include "State one's held view" , "Give one's view" , "Express a point of view" , "Express one's opinion openly" , "Say what one thinks" .)