Unfriendly, possibly rash hothead (5)
I believe the answer is:
harsh
'unfriendly' is the definition.
(thesaurus)
'possibly rash hothead' is the wordplay.
'possibly' indicates anagramming the letters.
'hothead' becomes 'h' (head letter of 'hot').
'rash' anagrammed gives 'hars'.
'hars'+'h'='HARSH'
(Other definitions for harsh that I've seen before include "Draconian" , "Strict, unfair" , "Guttural" , "Jarring" , "Rough and disagreeable, maybe of voice" .)