When rook comes north, catch sound of larger bird (4)
I believe the answer is:
rhea
'bird' is the definition.
(I know that rhea is a type of ratite)
'when rook comes north catch sound of larger' is the wordplay.
I cannot quite understand how this works, but
'when' could be 'e' (I've seen this in other clues) and 'e' is located in the answer.
'rook' could be 'r' (chess abbreviation) and 'r' is found within the answer.
The remaining letters 'ha' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rhea that I've seen before include "Flightless bird from South America" , "Big bird" , "Ostrich-like bird of South America" , "Moon" , "Small 'ostrich'" .)