In endless crawl, old wino consumed oily liquid (8)
I believe the answer is:
creosote
'oily liquid' is the definition.
(liquid made from oil)
'in endless crawl old wino' is the wordplay.
'in' is an insertion indicator.
'endless' means to remove the last letter.
'crawl' becomes 'creep' (synonyms).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'wino' becomes 'sot' (both can mean someone who drinks too much).
'creep' with its final letter removed is 'cree'.
'o'+'sot'='osot'
'cree' going around 'osot' is 'CREOSOTE'.
'consumed' is the link.
I am not very happy about this link. It may belong to another bit of the clue.
(Other definitions for creosote that I've seen before include "Dark oily liquid, preservative for wood" , "Wood treatment" , "Wood-preserving oil" , "Wood preservative oil" , "Oily liquid obtained from tar" .)