Remoulded spares coming round have to meet a required standard (4,6)
I believe the answer is:
pass muster
'meet a required standard' is the definition.
(something which passes muster meets a standard)
'remoulded spares coming round have' is the wordplay.
'remoulded' indicates anagramming the letters.
'coming round' is an insertion indicator.
'have' becomes 'must' (synonyms).
'spares' with letters rearranged gives 'passer'.
'passer' going around 'must' is 'PASS MUSTER'.
'to' is the link.
(Other definitions for pass muster that I've seen before include "Satisfy, suffice" , "Be good enough" , "appear acceptable" , "To fit the bill" .)