Picks up supporters by end of pier (7)
I believe the answer is:
rallies
'picks up' is the definition.
The definition and answer can be both related to change as well as being verbs in their -s form.
Maybe you can see an association between them that I can't see?
'supporters by end of pier' is the wordplay.
'supporters' becomes 'allies' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'end of pier' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'allies' put after 'r' is 'RALLIES'.
Can you help me to learn more?
(Other definitions for rallies that I've seen before include "Recovers in health" , "Extended exchanges of tennis strokes" , "Car races on public roads" , "court exchanges?" , "Mobilizes" .)