Moderates see a reforming Socialist leader (5)
I believe the answer is:
eases
'moderates' is the definition.
(moderate can mean to ease or relieve)
'see a reforming socialist leader' is the wordplay.
'reforming' indicates an anagram.
'leader' suggests taking the first letters.
The first letter of 'socialist' is 's'.
'see'+'a'='seea'
'seea' anagrammed gives 'ease'.
'ease'+'s'='EASES'
(Other definitions for eases that I've seen before include "Makes more comfortable" , "Makes less severe" , "Lessens tensions" , "Assuages or slackens" , "Relieves, loosens" .)