Secret city shelter (6)
I believe the answer is:
latent
'secret' is the definition.
(thesaurus)
'city shelter' is the wordplay.
'city' becomes 'LA' (Los Angeles).
'shelter' becomes 'tent' (canvas shelter).
'la'+'tent'='LATENT'
(Other definitions for latent that I've seen before include "Talent (anag)" , "Not presently active" , "'Hidden, undeveloped (6)'" , "Potential, dormant" , "Concealed - not yet developed" .)