Cleaner welcomes current president (5)
I believe the answer is:
chair
'president' is the definition.
(I know that president can be written as chair)
'cleaner welcomes current' is the wordplay.
'cleaner' becomes 'char' (char can mean a cleaner).
'welcomes' is an insertion indicator (in sense of 'invites in').
'current' becomes 'I' (physics symbol).
'char' enclosing 'i' is 'CHAIR'.
(Other definitions for chair that I've seen before include "Top seat of committee" , "academic office" , "Backed seat for one" , "See 4" , "Preside over - seat" .)