Sheltered spot housing mongrel (6)
I believe the answer is:
secure
'sheltered' is the definition.
('secure' can be similar in meaning to 'sheltered')
'spot housing mongrel' is the wordplay.
'spot' becomes 'see' (I've seen this before).
'housing' indicates putting letters inside.
'mongrel' becomes 'cur' ('cur' can be a synonym of 'mongrel').
'see' placed around 'cur' is 'SECURE'.
(Other definitions for secure that I've seen before include "Firmly in place - free from danger" , "Safe, free from danger" , "Make safe or fasten" , "Seize; make fast" , "Rescue (anag) - make safe" .)