Intend to be unpleasant (4)
I believe the answer is:
mean
I believe this clue is a double definition.
'intend' is the first definition.
(I know that intend can be written as mean)
'be unpleasant' is the second definition.
(thesaurus)
'to' acts as a link.
(Other definitions for mean that I've seen before include "Unkind; average" , "middle course" , "Intend; unkind" , "show" , "intimate" .)