Army detachment uncovered large towns' wicked deeds (10)
I believe the answer is:
atrocities
'wicked deeds' is the definition.
'army detachment uncovered large towns'' is the wordplay.
'army detachment' becomes 'atr' (I can't justify this - if you can you should give a lot more credence to this answer).
'uncovered' means to look at the middle letters.
'large' becomes 'well-rounded'.
'towns'' becomes 'cities'.
The middle of 'wellrounded' is 'o'.
'atr'+'o'+'cities'='ATROCITIES'
Can you help me to learn more?
(Other definitions for atrocities that I've seen before include "barbarous acts" , "Awful acts" .)