Tense request for a piece of work (4)
I believe the answer is:
task
'a piece of work' is the definition.
(thesaurus)
'tense request' is the wordplay.
'tense' becomes 't' (abbreviation used in many dictionaries).
'request' becomes 'ask' ('ask' can be a synonym of 'request').
't'+'ask'='TASK'
'for' is the link.
(Other definitions for task that I've seen before include "Burden with work" , "commission" , "Set piece of work" , "Errand, duty" , "Arduous bit of work" .)