The leader requesting and requiring considerable labour (7)
I believe the answer is:
tasking
'requiring considerable labour' is the definition.
I can't tell whether this defines the answer.
'the leader requesting' is the wordplay.
'leader' says to take the initial letters.
'requesting' becomes 'asking' ('ask' can be a synonym of 'request').
The first letter of 'the' is 't'.
't'+'asking'='TASKING'
'and' is the link.
Can you help me to learn more?
(Other definitions for tasking that I've seen before include "piecework" , "Making great demands" .)