Quick-moving soldier in valley without leader (5)
I believe the answer is:
agile
'quick-moving' is the definition.
(I've seen this before)
'soldier in valley without leader' is the wordplay.
'soldier' becomes 'gi' (government issue or general issue).
'in' means one lot of letters goes inside another.
'valley' becomes 'dale' (dale is a kind of valley).
'without leader' means to remove the first letter.
'dale' with its first letter taken away is 'ale'.
'gi' put into 'ale' is 'AGILE'.
(Other definitions for agile that I've seen before include "Limber" , "Nimble, lively" , "Nimble, lithe" , "Mentally acute" , "Spry - energetic" .)