Support for Palestine's leader (4)
I believe the answer is:
prop
'support' is the definition.
(prop up can mean to support)
'for palestine's leader' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'leader' suggests taking the first letters.
The first letter of 'palestine' is 'p'.
'pro'+'p'='PROP'
(Other definitions for prop that I've seen before include "Shore for 4 down" , "Set piece" , "needed at certain stages" , "Seize and hold firmly" , "One is usually among the strongest and heaviest rugby players" .)