Expression of weariness coming from house on hill, mostly (5-2)
I believe the answer is:
heigh-ho
'expression of weariness' is the definition.
(expression used in exhaustion or resignation)
'house on hill mostly' is the wordplay.
'house' becomes 'ho' (abbreviation for house).
'on' means one lot of letters go next to another.
'hill' becomes 'height' (height can mean a hill or higher ground).
'mostly' means to remove the last letter.
'height' with its last letter removed is 'heigh'.
'ho' put after 'heigh' is 'HEIGH-HO'.
'coming from' acts as a link.
(Other definitions for heigh-ho that I've seen before include "Tired expression" , "Expression of resignation or boredom" , "''... ... it's home from work we go'' (Snow White and the 7 Dwarfs)" , "Gosh, I'm tired!" , "Weary expression" .)