Design fashionable shelter (6)
I believe the answer is:
intent
'design' is the definition.
(thesaurus)
'fashionable shelter' is the wordplay.
'fashionable' becomes 'in' ('in' can be similar in meaning to 'fashionable').
'shelter' becomes 'tent' (tent is a kind of shelter).
'in'+'tent'='INTENT'
(Other definitions for intent that I've seen before include "Eager" , "Purpose under canvas" , "'Engrossed, absorbed (6)'" , "Keen" , "With mind fixed on purpose, concentrated" .)