Man almost pleased to be an agitator (10)
I believe the answer is:
malcontent
'an agitator' is the definition.
(thesaurus)
'man almost pleased' is the wordplay.
'man' becomes 'male'.
'almost' means to remove the last letter (almost the whole word is kept).
'pleased' becomes 'content' (associated in meaning).
'male' with its last letter taken off is 'mal'.
'mal'+'content'='MALCONTENT'
'to be' is the link.
(Other definitions for malcontent that I've seen before include "moaner" , "Grumbler" , "disgruntled" , "Unhappy" , "trouble-maker" .)