Coaster, perhaps, with part of the mast missing (3)
I believe the answer is:
mat
'coaster' is the definition.
(I've seen this before)
'with part of the mast missing' is the wordplay.
'with' is a charade indicator (letters next to each other).
'part of' suggests taking the first letters (I've seen 'part' mean this).
'missing' becomes 'at' (I can't explain this - if you can you should give a lot more credence to this answer).
The first letter of 'mast' is 'm'.
'm'+'at' is 'MAT'.
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for mat that I've seen before include "Shoe-cleaner" , "Rug; without a shine" , "Foot-wiper on which welcome may be kept" , "Piece of material for wiping feet on" , "Dull, rug" .)