I'll get accommodation in the best possible quarters (7)
I believe the answer is:
billets
'quarters' is the definition.
('billet' can be a synonym of 'quarter')
'i'll get accommodation in' is the wordplay.
'get accommodation' becomes 'bets' (I can't justify this - if you can you should believe this answer much more).
'in' means one lot of letters goes inside another.
'ill' going inside 'bets' is 'BILLETS'.
'the best possible' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for billets that I've seen before include "Soldiers' lodgings" , "Lodgings for the military" .)