Carry forward, let's assume (4,2)
I believe the answer is:
take on
'assume' is the definition.
(I know that assume can be written as take on)
'carry forward let's' is the wordplay.
I cannot really understand how this works, but
'carry' could be 'take' (synonyms) and 'take' is present in the answer.
'forward' could be 'on' and 'on' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for take on that I've seen before include "Agree to do (a task)" , "Employ, or agree to play against" , "Engage employee or assume responsibility" , "recruit" , "Agree to do (something)" .)