Thus endlessly can provide shelter (3)
I believe the answer is:
hut
'shelter' is the definition.
(I know that hut is a type of shelter)
'thus endlessly can' is the wordplay.
'endlessly' means to remove the last letter.
'can' is an anagram indicator (I've seen 'canned' mean this (canned can mean drunk)).
'thus' with its final letter taken off is 'thu'.
'thu' anagrammed gives 'HUT'.
'provide' is the link.
(Other definitions for hut that I've seen before include "Small crudely-built shelter" , "Small roughly-made house or shelter" , "'Shack, hovel (3)'" , "Simple abode" , "Small, simple shelter" .)