Fitting carpet regularly (3)
I believe the answer is:
apt
'fitting' is the definition.
(I've seen this before)
'carpet regularly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'carpet' are 'APT'.
(Other definitions for apt that I've seen before include "apartment in Queens, say" , "Prone" , "Befitting" , "suitable for the circumstances" , "Proper" .)