Rock making pleasant sound (6)
I believe the answer is:
gneiss
'rock' is the definition.
(gneiss is a kind of rock)
'pleasant sound' is the wordplay.
'pleasant' becomes 'nice' ('nice' is associated in meaning with 'pleasant').
'sound' shows a homophone (sound like).
'nice' is a homophone of 'GNEISS'.
'making' acts as a link.
(Other definitions for gneiss that I've seen before include "Metamorphic rock" , "Coarse-grained rock; sounds like agreeable" .)