Wheel gets round mat (7)
I believe the answer is:
coaster
'mat' is the definition.
(I've seen this before)
'wheel gets round' is the wordplay.
'wheel' becomes 'caster' (small wheel attached to a large object).
'gets' indicates putting letters inside (gets can mean captures or absorbs).
'round' becomes 'o' (round can mean a round object).
'caster' going around 'o' is 'COASTER'.
(Other definitions for coaster that I've seen before include "Small mat for glass" , "Small ship or beer mat" , "Mat for decanter or glasses" , "... another one [VESSEL]" , "Small mat; cargo ship" .)