Spill from a keg ale, upset (7)
I believe the answer is:
leakage
'spill' is the definition.
(thesaurus)
'a keg ale upset' is the wordplay.
'upset' is an anagram indicator.
'a'+'keg'+'ale'='akegale'
'akegale' is an anagram of 'LEAKAGE'.
'from' is the link.
(Other definitions for leakage that I've seen before include "Gradual escape" , "Liquid lost" , "Discharge of fluid through a small gap" , "Percolation" , "Escape of liquid/gas" .)