'Spitting Image' somewhat left-wing? (4)
I believe the answer is:
twin
'spitting image' is the definition.
(thesaurus)
'somewhat left-wing?' is the wordplay.
'somewhat' indicates the answer is hidden within the clue.
'TWIN' is hidden in the letters of 'left wing'.
(Other definitions for twin that I've seen before include "One of two conceived together" , "One from double birth" , "One of two that match" , "This set is matching jumper and cardigan" , "One of two conceived simultaneously" .)