Mother embellished walls lining home to the utmost (9)
I believe the answer is:
damnedest
'the utmost' is the definition.
(I've seen this in another clue)
'mother embellished walls lining home' is the wordplay.
'mother' becomes 'dam' (female parent of an animal).
'walls' means to remove the middle letters (the walls are the letters on each edge).
'lining' indicates putting letters inside.
'home' becomes 'nest' (a bird's home).
'embellished' with its centre taken out is 'ed'.
'ed' going into 'nest' is 'nedest'.
'dam'+'nedest'='DAMNEDEST'
'to' is the link.
(Other definitions for damnedest that I've seen before include "The very best" , "Superlative effort" , "Maximum effort" .)