Emergency procedure if trial goes wrong (7)
I believe the answer is:
airlift
'emergency procedure' is the definition.
(I've seen this before)
'if trial goes wrong' is the wordplay.
'goes wrong' is an anagram indicator.
'if'+'trial'='iftrial'
'iftrial' with letters rearranged gives 'AIRLIFT'.
(Other definitions for airlift that I've seen before include "Rescue using planes" , "Flying transportation" , "delivery" , "(Emergency) flight" , "Emergency action by planes" .)