It may be beaten as mud dries out (4,4)
I believe the answer is:
side drum
'it may be beaten' is the definition.
The definition suggests a singular noun which matches the answer.
'mud dries out' is the wordplay.
'out' indicates an anagram (out can mean wrong or inaccurate).
'mud'+'dries'='muddries'
'muddries' is an anagram of 'SIDE-DRUM'.
'as' is the link.
Can you help me to learn more?
(Other definitions for side drum that I've seen before include "one's soundly beaten" , "One's struck by player" , "Instrument in the kitchen" , "Percussion instrument" .)