Just outside gym without concealment (6)
I believe the answer is:
openly
'without concealment' is the definition.
(I've seen this before)
'just outside gym' is the wordplay.
'just' becomes 'only' ('only' can be a synonym of 'just').
'outside' is an insertion indicator.
'gym' becomes 'pe'.
'only' enclosing 'pe' is 'OPENLY'.
(Other definitions for openly that I've seen before include "Above board" , "Without concealment, frankly" , "without secrecy" , "Candidly, without concealment." , "In candid, up-front manner" .)