Hook applauds pair at the bottom exchanging places (5)
I believe the answer is:
clasp
'hook' is the definition.
(I've seen this in another clue)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for clasp that I've seen before include "Grasp firmly" , "Close hands round" , "Grasp tightly" , "Fastening - firm grip" , "Grasp; fastener" .)