Undertaking convict’s last request (4)
I believe the answer is:
task
'undertaking' is the definition.
(I know that undertaking can be written as task)
'convict's last request' is the wordplay.
'last' indicates one should take the final letters.
'request' becomes 'ask' (to ask is to request something).
The last letter of 'convict' is 't'.
't'+'ask'='TASK'
(Other definitions for task that I've seen before include "Give mission" , "Allocate work" , "Errand, duty" , "Job of work" , "Burden with work" .)