Undertake to carry forward? (4,2)
I believe the answer is:
take on
'undertake' is the definition.
(I know that undertake can be written as take on)
'carry forward?' is the wordplay.
'carry' becomes 'take' (synonyms).
'forward?' becomes 'on'.
'take'+'on'='TAKE ON'
'to' acts as a link.
(Other definitions for take on that I've seen before include "Employ or confront" , "Employ or stand up to" , "Accept as a challenge" , "recruit" , "Engage employee or assume responsibility" .)