Above taking part in wildcat operations (4)
I believe the answer is:
Here is my best explanation:
'above' is the definition.
'part in wildcat operations' is the subsidiary indication.
'part in' indicates a hidden word.
'atop' can be found hidden inside 'wildcat operations'.
'taking' is the link.
(Other definitions for atop that I've seen before include "Surmounting", "Upon", "Above", "At the apex", "At the highest point of", "On the highest point", "On (poetic)", "On the summit of", "On the peak" and "Situated on".)