Irrational to get soldiers some pepper (7)
I believe the answer is:
pimento
'some pepper' is the definition.
(pimiento is a type of pepper)
'irrational to get soldiers' is the wordplay.
'irrational' becomes 'pi' (an irrational number).
'get' indicates putting letters inside.
'soldiers' becomes 'men' (men can mean a group of soldiers).
'pi'+'to'='pito'
'pito' going around 'men' is 'PIMENTO'.
(Other definitions for pimento that I've seen before include "Vegetable" , "Jamaica pepper" , "Type of pepper" , "Allspice - top mine (anag)" , "Spicy berries" .)