Let man creep off to get substitute (11)
I believe the answer is:
replacement
'substitute' is the definition.
('replacement' can be a synonym of 'substitute')
'let man creep off' is the wordplay.
'off' is an anagram indicator.
'let'+'man'+'creep'='letmancreep'
'letmancreep' is an anagram of 'REPLACEMENT'.
'to get' acts as a link.
(Other definitions for replacement that I've seen before include "Restoration - substitution" , "change" , "One superseding another" , "A substitute item" , "sub" .)