Cheer, on the road, a single frozen pellet (9)
I believe the answer is:
hailstone
'frozen pellet' is the definition.
(I've seen this before)
'cheer on the road a single' is the wordplay.
'cheer on' becomes 'hail' (I can't justify this - if you can you should give a lot more credence to this answer).
'the road' becomes 'st'.
'a single' becomes 'one' (a single thing - only one).
'hail'+'st'+'one'='HAILSTONE'
Can you help me to learn more?
(Other definitions for hailstone that I've seen before include "Small pellet of ice" , "sign of cold weather" , "one in the shower" , "drop of ice" , "Frozen pellet" .)