Glasses needed for acrobats (8)
I believe the answer is:
tumblers
This clue is a double definition.
'glasses' is the first definition.
(tumbler is a kind of glass)
'acrobats' is the second definition.
('tumbler' can be a synonym of 'acrobat')
'needed for' is the link.
(Other definitions for tumblers that I've seen before include "Acrobats and drinking vessels" , "gymnasts" , "Pigeons" , "Flat bottomed glasses" , "circus acts?" .)