Assumes, when one calls upon to bowl (4,2)
I believe the answer is:
puts on
'assumes' is the definition.
The answer and definition can be both related to change as well as being verbs in their -s form.
Maybe you can see a link between them that I can't see?
'when one calls upon to bowl' is the wordplay.
I cannot really see how this works, but
'when' could be 'on' (I've seen this in other clues) and 'on' is found within the answer.
The remaining letters 'puts' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for puts on that I've seen is " Dons".)