Turn, holding mug and a tumbler (7)
I believe the answer is:
acrobat
'tumbler' is the definition.
('acrobat' can be a synonym of 'tumbler')
'turn holding mug and a' is the wordplay.
'turn' becomes 'act' (theatre**).
'holding' indicates putting letters inside.
'mug' becomes 'rob' (I've seen this in other clues).
'and' means one lot of letters go next to another.
'rob'+'a'='roba'
'act' going around 'roba' is 'ACROBAT'.
(Other definitions for acrobat that I've seen before include "Gymnastic performer" , "User of five ac" , "flipper" , "One appearing head over heels" , "Spectacular gymnast" .)