Alf reassembled the personnel for Sir John (8)
I believe the answer is:
falstaff
'sir john' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I can't see?
'alf reassembled the personnel' is the wordplay.
'reassembled' is an anagram indicator.
'the personnel' becomes 'staff' (staff is a kind of personnel).
'alf' is an anagram of 'fal'.
'fal'+'staff'='FALSTAFF'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for falstaff that I've seen before include "Large Shakespearean character" , "Mendacious Shakespearean knight" , "big role at Stratford" , "Shakespeare's fat alcoholic knight" , "Fat, jolly and debauched Shakespearean" .)