New canteen about right for opening (8)
I believe the answer is:
entrance
'opening' is the definition.
(opening leading to a building)
'new canteen about right' is the wordplay.
'new' indicates anagramming the letters.
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'canteen' anagrammed gives 'entance'.
'entance' placed around 'r' is 'ENTRANCE'.
'for' acts as a link.
(Other definitions for entrance that I've seen before include "drawbridge?" , "An actor's coming on stage" , "Way in - hypnotise" , "seventeen [POSTERN], perhaps" , "Beguile" .)