Mark spoils carpet to an extent (4)
I believe the answer is:
scar
'mark' is the definition.
(synonyms)
'spoils carpet to an extent' is the wordplay.
'to an extent' indicates the answer is hidden within the clue.
'SCAR' can be found hidden inside 'spoils carpet'.
(Other definitions for scar that I've seen before include "Skin mark; bare crag" , "Mark of healed cut" , "Mark of old injury" , "evidence of damage" , "Old wound - bare cliff" .)