Case of Welshman bagging very wild dragon (6)
I believe the answer is:
wyvern
'dragon' is the definition.
(I've seen this before)
'case of welshman bagging very wild' is the wordplay.
'case of' says to hollow out the word (remove centre letters) (outsides of).
'bagging' is an insertion indicator (I've seen this in other clues).
'wild' indicates an anagram.
'welshman' with its centre taken out is 'wn'.
'very' anagrammed gives 'yver'.
'wn' enclosing 'yver' is 'WYVERN'.
(Other definitions for wyvern that I've seen before include "Heraldic winged monster" , "Heraldic form of dragon" , "In heraldry, a dragon with wings, two legs and a barbed tail" , "Heraldic dragon with two legs and two wings" , "Winged two-legged dragon (heraldry)" .)