Chatter behind gym, meeting American stars (7)
I believe the answer is:
pegasus
'stars' is the definition.
(constellation)
'chatter behind gym meeting american' is the wordplay.
'chatter' becomes 'gas' (I've seen this before).
'behind' means one lot of letters go next to another.
'gym' becomes 'pe'.
'meeting' means one lot of letters go next to another.
'american' becomes 'us'.
'gas' after 'pe' is 'pegas'.
'pegas'+'us'='PEGASUS'
(Other definitions for pegasus that I've seen before include "Exceptional horse" , "madeup creature" , "Flying horse of myth" , "Inspirational figure" , "Winged horse - constellation" .)