Army officer trapped in very steep refuge (7)
I believe the answer is:
shelter
'refuge' is the definition.
(thesaurus)
'army officer trapped in very steep' is the wordplay.
'army officer' becomes 'lt' (I've seen this in other clues).
'trapped in' means one lot of letters goes inside another.
'very steep' becomes 'sheer' (I've seen this before).
'lt' put into 'sheer' is 'SHELTER'.
(Other definitions for shelter that I've seen before include "Sanctuary, protection" , "Find refuge" , "Protection; charity for the homeless" , "Refuge or protective cover" , "Refuge; protect" .)