Mostly inspect floor for ring (6)
I believe the answer is:
canvas
'for ring' is the definition.
(thesaurus)
'mostly inspect floor' is the wordplay.
'mostly' means to remove the first letter (v).
'inspect' becomes 'scan' (to scan is to inspect or examine).
'floor' becomes 'vas' (I can't explain this - if you can you should give a lot more credence to this answer).
'scan' with its first letter taken away is 'can'.
'can'+'vas'='CANVAS'
Can you help me to learn more?
(Other definitions for canvas that I've seen before include "Fabric for sail, tent and painting" , "An artist paints on it" , "Painting base" , "Fabric for sail, tent and picture" , "Heavy, closely-woven fabric" .)