Noisily peck parts of rock crystal (6)
I believe the answer is:
quartz
'rock crystal' is the definition.
'quartz' can be an answer for 'crystal' (I've seen this before). I am unsure of the 'rock' bit.
'noisily peck parts' is the wordplay.
'noisily' shows a homophone (sound like).
'peck parts' becomes 'quarts' (I've seen this in another clue).
'quarts' sounds like 'QUARTZ'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for quartz that I've seen before include "Hard mineral in timepieces" , "Mineral used in modern timepieces" , "Hard mineral found in watches" , "Type of watch and crystal" , "Hard glossy mineral present in many rocks" .)