Keep firm grasp in wrestling (10)

I believe the answer is:
stronghold
But I can't explain it at all! Could you help me understand?
(Other definitions for stronghold that I've seen before include "Fortress" , "castle" , "Keep" , "Defence" .)

I believe the answer is:
stronghold
But I can't explain it at all! Could you help me understand?
(Other definitions for stronghold that I've seen before include "Fortress" , "castle" , "Keep" , "Defence" .)