Crowd beginning to reappear, enthralled by daring beachwear (6)
I believe the answer is:
throng
'crowd' is the definition.
(I know that throng is a more specific form of the action crowd)
'beginning to reappear enthralled by daring beachwear' is the wordplay.
'beginning to' suggests taking the first letters.
'enthralled by' is an insertion indicator ('enthral' can mean 'capture').
'daring beachwear' becomes 'thong' (I've seen this in another clue).
The first letter of 'reappear' is 'r'.
'r' inserted into 'thong' is 'THRONG'.
(Other definitions for throng that I've seen before include "Large packed crowd" , "Multitude" , "Large gathering of people" , "Densely packed crowd" , "Large crowd or host" .)