Lieutenant in rank finding protection (7)
I believe the answer is:
shelter
'protection' is the definition.
(I know that protection can be written as shelter)
'lieutenant in rank' is the wordplay.
'lieutenant' becomes 'lt' (abbreviation for lieutenant).
'in' means one lot of letters goes inside another.
'rank' becomes 'sheer' (as in sheer hypocrisy, rank hypocrisy etc).
'lt' placed inside 'sheer' is 'SHELTER'.
'finding' acts as a link.
(Other definitions for shelter that I've seen before include "Roof" , "Refuge, protection" , "Find refuge" , "Give protection" , "Housing or haven" .)