Small solid fragment of pottery (5)
I believe the answer is:
shard
'fragment of pottery' is the definition.
(I've seen this before)
'small solid' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'solid' becomes 'hard' (associated in meaning).
's'+'hard'='SHARD'
(Other definitions for shard that I've seen before include "Sharp piece of glass" , "Broken piece of a brittle artefact" , "Go well with; attire" , "Sharp glass fragment" , "Sliver of glass, etc" .)