Falls back in with commander and artist (7)
I believe the answer is:
niagara
'falls' is the definition.
(thesaurus)
'back in with commander and artist' is the wordplay.
'back' says the letters should be written backwards.
'with' means one lot of letters go next to another.
'commander' becomes 'aga' (I've seen this before**).
'and' says to put letters next to each other.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'in' backwards is 'ni'.
'ni'+'aga'+'ra'='NIAGARA'
(Other definitions for niagara that I've seen before include "it's quite a height" , "River flowing from Lake Erie into Lake Ontario" , "& 22 Down North American cascade" , "Great waterfalls on border of USA and Canada" , "Great waterfalls on US-Canada border" .)