A bird shielded by friend, protective (8)
I believe the answer is:
paternal
'protective' is the definition.
(I've seen this before)
'a bird shielded by friend' is the wordplay.
'bird' becomes 'tern' (tern is a kind of bird).
'shielded by' is an insertion indicator (I've seen this in other clues).
'friend' becomes 'pal' (pal can mean a friend).
'a'+'tern'='atern'
'atern' placed into 'pal' is 'PATERNAL'.
(Other definitions for paternal that I've seen before include "Dad's" , "Fatherly in prenatal manner" , "Characteristic of a father" , "Of one's father" , "Fatherly in prenatal way" .)