Take part in school sports sick (4)
I believe the answer is:
dope
'sick' is the definition.
The answer and definition can be both related to bodily activities as well as being verbs in their base form.
Perhaps you can see an association between them that I can't see?
'take part in school sports' is the wordplay.
I cannot really understand how this works, but
'take' could be 'do' (eg taking or doing drugs) and 'do' is located in the answer.
'sports' could be 'pe' (Physical Education) and 'pe' is located in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for dope that I've seen before include "Lowdown; drugs (informal)" , "One simple" , "Idiot; information" , "Simpleton" , "Weed perhaps" .)