Old reliable with coastal wartime housing (8)
I believe the answer is:
stalwart
'old reliable' is the definition.
(stalwart can mean a reliable or loyal person)
'with coastal wartime housing' is the wordplay.
'housing' indicates the answer is hidden within the clue (part of the clue houses the answer).
'STALWART' is hidden within 'with coastal wartime'.
(Other definitions for stalwart that I've seen before include "Loyal, reliable and hardworking" , "Determined" , "Staunch; loyal" , "Committed" , "Staunch supporter" .)