Barely any road cycling before a drink - spill each one (1,4,2,3,5)
I believe the answer is:
a drop in the ocean
'barely any' is the definition.
'road cycling before a drink spill each one' is the wordplay.
'cycling' indicates an anagram.
'before' is a charade indicator (letters next to each other).
'a drink' becomes 'pint' (I've seen this before**).
'spill' indicates an anagram.
'road' is an anagram of 'adro'.
'each'+'one'='eachone'
'eachone' anagrammed gives 'heocean'.
'adro'+'pint'+'heocean'='A DROP IN THE OCEAN'
(Other definitions for a drop in the ocean that I've seen before include "Drink for a drifter" , "Certainly no effect of global warming" , "Very little indeed" , "something insignificant" , "A fall in sea level" .)