Mrs Capp joining Women's Movement (4)
I believe the answer is:
flow
'movement' is the definition.
(flow is a kind of movement)
'mrs capp joining' is the wordplay.
'mrs' becomes 'flo'.
'capp' becomes 'w' (I can't justify this - if you can you should give a lot more credence to this answer).
'joining' is a charade indicator (letters next to each other).
'flo'+'w'='FLOW'
'women's' acts as a link.
I am not very happy about this link. It may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for flow that I've seen before include "Scapa - , Orkney anchorage" , "Move steadily" , "Current" , "Run smoothly" , "Fluid motion" .)