Catch bird interrupting deliveries (8)
I believe the answer is:
overhear
'catch' is the definition.
('overhear' can be a synonym of 'catch')
'bird interrupting deliveries' is the wordplay.
'bird' becomes 'rhea' (rhea is a kind of bird**).
'interrupting' means one lot of letters goes inside another.
'deliveries' becomes 'over' (I've seen this before).
'rhea' going inside 'over' is 'OVERHEAR'.
(Other definitions for overhear that I've seen before include "Accidentally discover" , "Tune in to conversation accidentally" , "Listen without the speaker's knowledge, maybe by accident" , "Pick up" , "Accidentally perceive with the ear" .)