The doctor is not well for workout (5)
I believe the answer is:
drill
'for workout' is the definition.
(I've seen this in another clue)
'the doctor is not well' is the wordplay.
'the doctor' becomes 'Dr' (abbreviation).
'is not well' becomes 'ill' ('ill' is the opposite to 'well').
'dr'+'ill'='DRILL'
(Other definitions for drill that I've seen before include "training exercise" , "Monkey" , "Bore (a hole); fabric" , "DIY tool" , "Tool; fabric; bore" .)