Needing support, Bolshevik leader turns to Left (7)
I believe the answer is:
lacking
'needing' is the definition.
(thesaurus)
'support bolshevik leader turns to left' is the wordplay.
I cannot quite see how this works, but
'leader' could be 'king' (King is an example) and 'king' is present in the answer.
'left' could be 'l' (common abbreviation) and 'l' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lacking that I've seen before include "Deficient or inadequate" , "'Deficient, wanting (7)'" , "Short" , "Missing" , "Absent, deficient" .)