Painful losing head on slippery stones - they sound quite piercing (8)
I believe the answer is:
screechy
'piercing' is the definition.
(thesaurus)
'painful losing head on slippery stones' is the wordplay.
'painful' becomes 'achy' (similar in meaning).
'losing head' means to remove the first letter.
'on' means one lot of letters go next to another.
'slippery stones' becomes 'scree' (scree is a mass of loose rocks on a mountain. I am not sure about the 'slippery' bit.).
'achy' with its initial letter taken away is 'chy'.
'chy' put after 'scree' is 'SCREECHY'.
'they sound quite' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for screechy that I've seen before include "Shrieky" , "Loud, harsh, piercing" , "Raucous" , "Making harsh and piercing cries" , "Crying loudly" .)