Number of US soldiers in retreat making an impression (6)
I believe the answer is:
signet
'an impression' is the definition.
(thesaurus)
'number of us soldiers in retreat' is the wordplay.
'number of' becomes 'ten' (I can't explain this - if you can you should give a lot more credence to this answer).
'us soldiers' becomes 'gis' (GI, nickname for US soldier).
'in retreat' says the letters should be written in reverse.
'ten'+'gis'='tengis'
'tengis' written backwards gives 'SIGNET'.
'making' acts as a link.
Can you help me to learn more?
(Other definitions for signet that I've seen before include "Small seal sounds like a young swan" , "Tuft of hanging threads" , "Official seal" , "Tinges (anag) - seal" , "Ingest (anag)" .)