Hard to please in house: comfortable outside (6)
I believe the answer is:
choosy
'hard to please' is the definition.
(thesaurus)
'house comfortable outside' is the wordplay.
'house' becomes 'ho' (abbreviation for house).
'comfortable' becomes 'cosy' ('cosy' can be similar in meaning to 'comfortable').
'outside' indicates putting letters inside.
'ho' placed into 'cosy' is 'CHOOSY'.
'in' acts as a link.
(Other definitions for choosy that I've seen before include "Picky or particular" , "Overly fastidious" , "Fastidious, finicky" , "Difficult to please" , "Selective" .)