Upper-class fool in group of soldiers? (4)
I believe the answer is:
unit
'group of soldiers?' is the definition.
(unit can mean a group of soldiers)
'upper-class fool' is the wordplay.
'upper-class' becomes 'u' (similar in meaning).
'fool' becomes 'nit' (both can mean a stupid person).
'u'+'nit'='UNIT'
'in' is the link.
(Other definitions for unit that I've seen before include "Single piece - kitchen cabinet" , "Detachment of soldiers" , "Kitchen fitting" , "Individual thing, single and complete" , "Small military detachment" .)