Sensitive cry of pain in extremes of treachery (6)
I believe the answer is:
touchy
'sensitive' is the definition.
(similar in meaning)
'cry of pain in extremes of treachery' is the wordplay.
'cry of pain' becomes 'ouch' (exclamation said when in pain).
'in' indicates putting letters inside.
'extremes of' says to hollow out the word (remove centre letters) (only the letters at the extremes of the word).
'treachery' with its centre removed is 'ty'.
'ouch' placed into 'ty' is 'TOUCHY'.
(Other definitions for touchy that I've seen before include "Ticklish" , "Quick to take offence" , "Thin-skinned, easily offended" , "Quick-tempered" , "Irritable" .)