The frequent practice of riding? (5)
I believe the answer is:
habit
'the frequent practice' is the definition.
'habit' can be an answer for 'practice' (habit is a kind of practice). I am unsure of the 'the frequent' bit.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for habit that I've seen before include "Ingrained behaviour" , "Addiction to a drug" , "can cause addiction" , "Custom - costume" , "Custom; riding dress" .)