Conjuring soldier in coat (5)
I believe the answer is:
magic
'conjuring' is the definition.
(I've seen this before)
'soldier in coat' is the wordplay.
'soldier' becomes 'GI' (term for US soldier).
'in' indicates putting letters inside.
'coat' becomes 'mac' (mac is a kind of coat).
'gi' put within 'mac' is 'MAGIC'.
(Other definitions for magic that I've seen before include "'Charms, spells, illusions (5)'" , "Conjuror's art" , "Illusory feat" , "Spelling?" , "Art that supposedly invokes supernatural powers" .)