Work on central heating, as you choose (3)
I believe the answer is:
opt
'choose' is the definition.
(thesaurus)
'work on central heating' is the wordplay.
'work' becomes 'op' (abbreviation for opus).
'on' is a charade indicator (letters next to each other).
'central' means to look at the middle letters.
The middle of 'heating' is 't'.
'op'+'t'='OPT'
'as you' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for opt that I've seen before include "End or act of shutting" , "Make a choice" , "Pick from pot" , "Prefer, choose" , "Plump for" .)