Frank is the one staggering round the piano (4)
I believe the answer is:
open
'frank' is the definition.
('open' can be a synonym of 'frank')
'the one staggering round the piano' is the wordplay.
'staggering' is an anagram indicator.
'round' is an insertion indicator.
'the piano' becomes 'p'.
'one' with letters rearranged gives 'oen'.
'oen' enclosing 'p' is 'OPEN'.
'is' acts as a link.
(Other definitions for open that I've seen before include "Plain" , "Available for business, exposed" , "Exposed; free" , "simple" , "Liberal" .)