Source of tar or possibly some alcohol (4)
I believe the answer is:
coal
This clue could be a double definition.
'source of tar' is the first definition.
'coal' can be an answer for 'tar' (thesaurus). I'm unsure of the 'source of' bit.
'possibly some alcohol' is the second definition.
'coal' can be an answer for 'alcohol' (thesaurus). I'm not certain of the 'possibly some' bit.
'or' is the link.
Can you help me to learn more?
(Other definitions for coal that I've seen before include "Carbonized vegetable matter" , "This consists mainly of carbon" , "slack" , "Mined fuel" , "Char" .)