Allowed occupancy of some billets
I believe the answer is:
let
'allowed occupancy' is the definition.
'let' can be an answer for 'allowed' (to let is to allow or permit). I'm not sure about the 'occupancy' bit.
'some billets' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'LET' is hidden in the letters of 'billets'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for let that I've seen before include "Award (a contract)" , "Rent out (property)" , "Allow; rental period" , "Rent out: grant" , "Allow; leased" .)