Power of leader of Socialist Party? (5)
I believe the answer is:
steam
'power' is the definition.
(I've seen this before)
'leader of socialist party?' is the wordplay.
'leader of' suggests taking the first letters.
'party?' becomes 'team' (both can mean a group of people).
The first letter of 'socialist' is 's'.
's'+'team'='STEAM'
'of' is the link.
(Other definitions for steam that I've seen before include "Gas formed by vaporizing water at 100?C" , "Water-vapour" , "Driving force" , "A lot of hot air" , "comes with a hiss?" .)