Chum put down floor covering, interrupting exercise (8)
I believe the answer is:
playmate
'chum' is the definition.
(thesaurus)
'put down floor covering interrupting exercise' is the wordplay.
'put down' becomes 'lay' ('lay' can be a synonym of 'put down').
'floor covering' becomes 'mat' (mat is a kind of floor covering).
'interrupting' means one lot of letters goes inside another.
'exercise' becomes 'pe' (Physical Education).
'lay'+'mat'='laymat'
'laymat' placed within 'pe' is 'PLAYMATE'.
(Other definitions for playmate that I've seen before include "Child's companion" , "fun chum" , "My palate (anag.)" , "Child's friend" , "Chum in recreation" .)