Thanks for the suggestion - I do know that the correct answer has two headwords in Chambers, and that the first has 6 definitions, of which REAR and BIRD are just two. This rules out bunting I'm afraid.
I apologise to you both - I was on completely the wrong track with REAR and BIRD, having been mislead by the puzzle's preamble, and so set an unsolvable question.
Thank you again for your contributions.