Jack comically takes a bit of exercise pushing back cover (8)
I believe the answer is:
deputise
'pushing back cover' is the definition.
The definition and answer can be both to do with social activities as well as being verbs in their base form.
Maybe there's an association between them I don't understand?
'jack comically takes a bit of exercise' is the wordplay.
I cannot quite understand how this works, but
'takes' could be 'is' (being is a kind of taking) and 'is' is located in the answer.
The remaining letters 'depute' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for deputise that I've seen before include "Understudy" , "Appoint as representative" , "Act as delegate for a person" , "Stand in for" , "Appoint as stand-in" .)