Squadron, say, drops one veteran without number (6)
I believe the answer is:
untold
'without number' is the definition.
(thesaurus)
'squadron say drops one veteran' is the wordplay.
'squadron say' becomes 'unit' (squadron is a kind of unit).
'drops' indicates named letters should be taken away.
'one' becomes 'I' (Roman numeral).
'veteran' becomes 'old' (I've seen this in another clue).
'unit' with 'i' removed is 'unt'.
'unt'+'old'='UNTOLD'
(Other definitions for untold that I've seen before include "Lots" , "Not disclosed - fabulous!" , "missing relations" , "Not narrated or measured" , "enormous" .)