Fatherly friend keeps a bird (8)
I believe the answer is:
paternal
'fatherly' is the definition.
(similar in meaning)
'friend keeps a bird' is the wordplay.
'friend' becomes 'pal' (pal is a kind of friend).
'keeps' means one lot of letters goes inside another.
'bird' becomes 'tern' (tern is a kind of bird).
'a'+'tern'='atern'
'pal' going around 'atern' is 'PATERNAL'.
(Other definitions for paternal that I've seen before include "Of one's father" , "Characteristic of a father" , "protective interest" , "Fatherly in prenatal way" , "Dad's" .)