A thousand winged creatures seen around in the morning — they are huge (8)
I believe the answer is:
mammoths
'they are huge' is the definition.
(mammoths were huge animals)
'a thousand winged creatures seen around in the morning' is the wordplay.
'a thousand' becomes 'M' (Roman numeral for a thousand).
'winged creatures' becomes 'moths' (moths are winged insects).
'seen around' indicates putting letters inside.
'in the morning' becomes 'am' (AM on a clock).
'm'+'moths'='mmoths'
'mmoths' placed around 'am' is 'MAMMOTHS'.
(Other definitions for mammoths that I've seen before include "Extinct elephants with hairy coats" , "Ancient hairy elephants" , "Extinct large hairy elephants" , "enormous creatures!" , "old jumbos" .)