Horse rearing upset angry-looking bird (6)
I believe the answer is:
gander
'looking bird' is the definition.
'gander' can be an answer for 'bird' (gander is a kind of bird). I am unsure of the 'looking' bit.
'horse rearing upset angry' is the wordplay.
'horse' becomes 'nag' (nag is a kind of horse).
'rearing' is a reversal indicator (as in a horse rearing up).
'upset' says the letters should be written in reverse.
'angry' becomes 'red' (I've seen this in other clues).
'nag' back-to-front is 'gan'.
'red' in reverse letter order is 'der'.
'gan'+'der'='GANDER'
Can you help me to learn more?
(Other definitions for gander that I've seen before include "Butchers - goose" , "Goose sauce is good for it" , "male member of the Anatidae family" , "glance" , "Ranged about with male goose" .)