Faster fastener needed on the wharf (7)
I believe the answer is:
'faster' is the definition.
Both the answer and definition are comparative adjectives. Maybe they are linked in a way I don't understand?
'fastener needed on the wharf' is the wordplay.
'fastener' becomes 'zip' (zip is a kind of fastener).
'needed on' is a charade indicator (letters next to each other) (in a down clue, some letters go on top of others).
'the wharf' becomes 'pier' (I've seen this before).
Can you help me to learn more?