A soldier thanks man, flustered (8)
I believe the answer is:
agitated
'flustered' is the definition.
(thesaurus)
'a soldier thanks man' is the wordplay.
'soldier' becomes 'GI' (GI can mean a US soldier).
'thanks' becomes 'ta' (UK informal version of 'thank you').
'man' becomes 'ted' (Ted is a man's name).
'a'+'gi'+'ta'+'ted'='AGITATED'
(Other definitions for agitated that I've seen before include "Upset, disturbed" , "Distressed" , "Troubled, perturbed" , "Aroused - disturbed" , "Upset (by a stirrer?)" .)