Pa learnt to be fatherly (8)
I believe the answer is:
paternal
'fatherly' is the definition.
(similar in meaning)
'pa learnt to be' is the wordplay.
'to be' indicates an anagram.
'learnt' is an anagram of 'ternal'.
'pa'+'ternal'='PATERNAL'
(Other definitions for paternal that I've seen before include "Fatherly in prenatal manner" , "Of one's father" , "Characteristic of a father" , "Fatherly in prenatal way" , "Related on the father's side" .)