Poems soldiers occasionally used (4)
I believe the answer is:
odes
'poems' is the definition.
(ode is a kind of poem)
'soldiers occasionally used' is the wordplay.
'occasionally used' indicates alternate letters.
The alternating letters of 'soldiers' are 'ODES'.
(Other definitions for odes that I've seen before include "Keats was fond of them" , "poetry" , "Lays" , "Lyric poems" , "Poets write them" .)