Bird, the reverse of animal with intelligence (6)
I believe the answer is:
godwit
'bird' is the definition.
(godwit is a kind of bird)
'reverse of animal with intelligence' is the wordplay.
'reverse of' says the letters should be written in reverse.
'animal' becomes 'dog' (type of animal).
'with' is a charade indicator (letters next to each other).
'intelligence' becomes 'wit' (wit is a kind of intelligence).
'dog' back-to-front is 'god'.
'god'+'wit'='GODWIT'
'the' is the link.
(Other definitions for godwit that I've seen before include "Long-billed wader" , "Long-legged northern shore bird" , "Wader; do twig (anag.)" , "Large wading bird" , "Wader; two dig (anag.)" .)