Reptile accompanying American flower (6)
I believe the answer is:
crocus
'flower' is the definition.
(I've seen this before)
'reptile accompanying american' is the wordplay.
'reptile' becomes 'croc' (short for crocodile).
'accompanying' means one lot of letters go next to another.
'american' becomes 'US' (United States).
'croc'+'us'='CROCUS'
(Other definitions for crocus that I've seen before include "Early flowering bulb" , "Yellow, purple or white spring flower" , "Small plant with yellow, purple or white flowers" , "Spring-flowering plant" , "Spring plant" .)