Toy goblin: beastly, empty junk (10)
I believe the answer is:
hobbyhorse
'toy' is the definition.
(hobbyhorse is a kind of toy)
'goblin beastly empty junk' is the wordplay.
'goblin' becomes 'hob' ('hob' can be a synonym of 'goblin').
'empty' suggests removing the centre.
'junk' becomes 'horse' ('horse' can be a synonym of 'junk'**).
'beastly' with its middle removed is 'by'.
'hob'+'by'+'horse'='HOBBYHORSE'
(Other definitions for hobbyhorse that I've seen before include "Toy" , "plaything" .)