Exercised and entertained, but not in the morning (4)
I believe the answer is:
used
'exercised' is the definition.
(thesaurus)
'entertained but not in the morning' is the wordplay.
'entertained' becomes 'amused' (amusing is a kind of entertaining).
'but not' indicates named letters should be taken away.
'in the morning' becomes 'am'.
'amused' with 'am' removed is 'USED'.
'and' acts as a link.
(Other definitions for used that I've seen before include "Scottish expert" , "not got directly" , "Brought into play" , "like majority of cars?" , "Not fresh" .)