America developing muscle and losing Democrat (5,3)
I believe the answer is:
uncle sam
'america' is the definition.
(I've seen this before)
'developing muscle and losing democrat' is the wordplay.
'developing' indicates anagramming the letters.
'losing' is a deletion indicator.
'democrat' becomes 'd'.
'muscle'+'and'='muscleand'
'muscleand' with 'd' taken away is 'musclean'.
'musclean' with letters rearranged gives 'UNCLE SAM'.
(Other definitions for uncle sam that I've seen before include "Clue's man? (anag)" , "Iconic American male relative" , "USA personified" , "Personification of the States" , "national representative, initially appropriate" .)