Rue letting go royal bird (5)
I believe the answer is:
egret
'bird' is the definition.
(egret is a kind of bird)
'rue letting go royal' is the wordplay.
I cannot quite see how this works, but
'royal' could be 'r' (abbreviation) and 'r' is found in the answer.
'go' could be 'get' (synonyms) and 'get' is located in the remaining letters.
A single letter 'e' remains which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for egret that I've seen before include "Long-plumed heron" , "(Usually) white heron" , "Wader with white plumage" , "Bird eating fish" , "Greet (anag) -- wading bird" .)