Understanding French in shelter possible at last (7)
I believe the answer is:
entente
'understanding' is the definition.
(an entente is an alliance or understanding)
'french in shelter possible at last' is the wordplay.
'french in' becomes 'en' (French for 'in').
'shelter' becomes 'tent' (canvas shelter).
'at last' indicates one should take the final letters.
The final letter of 'possible' is 'e'.
'en'+'tent'+'e'='ENTENTE'
(Other definitions for entente that I've seen before include "friendly relations" , "Friendly arrangement" , "Friendly understanding between states" , "A friendly understanding between countries, may be cordial" , "that brings nations closer together" .)