Cricket side ready for attack (5)
I believe the answer is:
onset
'attack' is the definition.
(synonyms)
'cricket side ready' is the wordplay.
'cricket side' becomes 'on' (cricket term, on or leg side).
'ready' becomes 'set' (synonyms).
'on'+'set'='ONSET'
'for' acts as a link.
(Other definitions for onset that I've seen before include "Appearance of" , "origin" , "Initial stage; attack" , "Assault; start" , "Outbreak" .)