Perhaps I damaged precious stone (8)
I believe the answer is:
sapphire
'precious stone' is the definition.
(I've seen this before)
'perhaps i damaged' is the wordplay.
'damaged' indicates an anagram.
'perhaps'+'i'='perhapsi'
'perhapsi' with letters rearranged gives 'SAPPHIRE'.
(Other definitions for sapphire that I've seen before include "precious item" , "Deep blue colour" , "A gem; I, perhaps (anag.)" , "Blue gem" , "Corundum gemstone" .)