Dry run cancelled: help! (3)
I believe the answer is:
aid
'help' is the definition.
(synonyms)
'dry run cancelled' is the wordplay.
'dry' becomes 'arid' (similar in meaning).
'run' becomes 'r' (cricket abbreviation).
'cancelled' indicates named letters should be taken away.
'arid' with 'r' taken away is 'AID'.
(Other definitions for aid that I've seen before include "Help, assistance" , "Relief" , "Help. Assist" , "welfare" , "grant" .)