Mother still turned up being friendly (5)
I believe the answer is:
matey
'friendly' is the definition.
(similar in meaning)
'mother still turned up' is the wordplay.
'mother' becomes 'ma' (Ma is another word for mother or mum).
'still' becomes 'yet' (yet can mean still or so far).
'turned up' shows that the letters should be reversed in order.
'yet' backwards is 'tey'.
'ma'+'tey'='MATEY'
'being' acts as a link.
(Other definitions for matey that I've seen before include "Chummy" , "Sunshine" , "uncomfortably friendly" , "Friendly, sociable" , "Pally" .)