Colourful fish that may lead one on a wild goose chase (3,7)
I believe the answer is:
'lead one on a wild goose chase' is the definition.
'red herring' can be an answer for 'lead' (I have seen 'False lead ' mean 'red herring' so perhaps 'lead' could also mean 'red herring'). I am not sure about the 'one on a wild goose chase' bit.
'colourful fish that' is the wordplay.
I cannot quite understand how this works, but
'colourful' could be 'red' (similar in meaning) and 'red' is found within the answer.
'fish' could be 'herring' (herring is a kind of fish) and 'herring' is found in the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
'may' acts as a link.
Can you help me to learn more?
(Other definitions for red herring that I've seen before include "It may well put you off" , "Distraction" , "(Fishy) diversion" , "Cover" , "food?" .)