A spell in the Dutch army (5)
I believe the answer is:
charm
'a spell' is the definition.
(a charm is a magic spell)
'in the dutch army' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CHARM' can be found hidden inside 'dutch army'.
(Other definitions for charm that I've seen before include "Lure" , "Amulet; attractive quality" , "Personal attractiveness and charisma" , "Delight; magical object" , "Spell; ornament" .)