Power, say, linked with a small American group of stars (7)
I believe the answer is:
pegasus
'group of stars' is the definition.
(I've seen this before)
'power say linked with a small american' is the wordplay.
'power' becomes 'p' (symbol in physics).
'say' becomes 'eg' (both can mean 'for example').
'linked with' says to put letters next to each other.
'small' becomes 's' (abbreviation - e.g. clothes size).
'american' becomes 'US' (United States).
'p'+'eg'+'a'+'s'+'us'='PEGASUS'
(Other definitions for pegasus that I've seen before include "Inspirational figure" , "Northern hemisphere constellation - use gaps (anag)" , "mount in the clouds" , "Mount flying" , "Flying horse of myth" .)