Gardener confused about one military man (9)
I believe the answer is:
grenadier
'military man' is the definition.
(grenadier is a kind of military man)
'gardener confused about one' is the wordplay.
'confused' indicates anagramming the letters.
'about' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'gardener' is an anagram of 'grenader'.
'grenader' going around 'i' is 'GRENADIER'.
(Other definitions for grenadier that I've seen before include "bomb-thrower" , "African flier" , "A household infantryman" , "historical bomber" , "Infantryman - in red gear (anag)" .)