Source of heating abandoned by British tanker (5)
I believe the answer is:
oiler
'tanker' is the definition.
(I know that tanker can be written as oiler)
'source of heating abandoned by british' is the wordplay.
'source' says to take the initial letters (I've seen 'sources of' mean this (the beginning of a word is its sauce)).
'heating abandoned by british' becomes 'iler' (I am not sure about this - if you are sure you should believe this answer much more).
The first letter of 'of' is 'o'.
'o'+'iler'='OILER'
Can you help me to learn more?
(Other definitions for oiler that I've seen before include "it may be 4 [SHIPSHAPE]" , "Grease monkey" , "Loire (anag.)" , "Chippendales assistant?" , "One applying lubricant" .)