Group hanky-panky gets offensive (6)
I believe the answer is:
sextet
'group' is the definition.
The answer is an example.
'hanky-panky gets offensive' is the wordplay.
'hanky-panky' becomes 'sex' (I've seen this before).
'gets' says to put letters next to each other.
'offensive' becomes 'tet' (Tet Offensive, Vietnam War military campaign).
'sex'+'tet'='SEXTET'
(Other definitions for sextet that I've seen before include "Half-dozen in a group" , "band" , "Musical group" , "Group of six players" , "Group of six performers" .)