Old record used in Act I's clumsily cleaned up for theatre (7)
I believe the answer is:
aseptic
'cleaned up for theatre' is the definition.
(the edge letters or 'banks' are removed)
'old record used in act i's clumsily' is the wordplay.
'old record' becomes 'EP' (abbreviation for extended play record).
'used in' indicates putting letters inside.
'clumsily' indicates anagramming the letters.
'act'+'is'='actis'
'actis' with letters rearranged gives 'astic'.
'ep' going inside 'astic' is 'ASEPTIC'.
(Other definitions for aseptic that I've seen before include "Sterile" , "Germ-free" , "Paciest (anag.)" , "Free from harmful bacteria" , "Free from bacteria, surgically clean" .)