African starling’s quick bite concealed by high fence (8)
I believe the answer is:
oxpecker
'african starling's' is the definition.
(bird native to Africa)
'quick bite concealed by high fence' is the wordplay.
'quick bite' becomes 'peck' (quick bite from a bird).
'concealed by' means one lot of letters goes inside another.
'high fence' becomes 'oxer' (fence for containing cattle).
'peck' going into 'oxer' is 'OXPECKER'.
(Other definitions for oxpecker that I've seen before include "African bird that eats parasites on cattle" , "Flighty type" , "Bird dining on beef" .)