Sad peacekeepers meeting dwarf (7)
I believe the answer is:
unhappy
'sad' is the definition.
(synonyms)
'peacekeepers meeting dwarf' is the wordplay.
'peacekeepers' becomes 'UN' (United Nations, peacekeeping organisation).
'meeting' is a charade indicator (letters next to each other).
'dwarf' becomes 'happy' (I've seen this before).
'un'+'happy'='UNHAPPY'
(Other definitions for unhappy that I've seen before include "Woeful" , "Not contented or peaceful" , "Sad, miserable" , "Sad, discontented" , "Unfortunate; miserable" .)