Tanker’s heating device with top blown off (5)
I believe the answer is:
oiler
'tanker's' is the definition.
(synonyms)
'heating device with top blown off' is the wordplay.
'heating device' becomes 'boiler'.
'with top blown off' means to remove the first letter.
'boiler' with its initial letter taken away is 'OILER'.
(Other definitions for oiler that I've seen before include "Loire (anag.)" , "Device that lubricates" , "Grease monkey" , "Petroleum tanker" , "One applying lubricant" .)