Fancies main track to go cycling (5)
I believe the answer is:
ideas
'fancies' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ideas that I've seen before include "Notions, concepts" , "Fancies" , "Aside (anag.)" , "Theories" , "Thoughts, maybe creative" .)