Loan a worker to help (4,1,4)
I believe the answer is:
lend a hand
'help' is the definition.
(thesaurus)
'loan a worker' is the wordplay.
'loan' becomes 'lend' ('lend' can be a synonym of 'loan').
'worker' becomes 'hand' (hand is a kind of worker).
'lend'+'a'+'hand'='LEND A HAND'
'to' is the link.
(Other definitions for lend a hand that I've seen before include "Give assistance" , "Pitch in" , "Provide help" , "To assist" , "temporarily transfer an employee" .)