Spiteful, but not initially irritated (5)
I believe the answer is:
itchy
'irritated' is the definition.
(an itch is a skin irritation)
'spiteful but not initially' is the wordplay.
'spiteful' becomes 'bitchy' (informal term).
'but not initially' means to remove the first letter.
'bitchy' with its initial letter removed is 'ITCHY'.
(Other definitions for itchy that I've seen before include "Affected by skin irritation" , "Wanting a scratch?" , "Unable to relax" , "Irritating to the skin" , "Tickling" .)