Three car makers organised test of public opinion (6,8)
I believe the answer is:
market research
'test of public opinion' is the definition.
The definition suggests a singular noun which matches the answer.
'three car makers organised' is the wordplay.
'organised' is an anagram indicator.
'three'+'car'+'makers'='threecarmakers'
'threecarmakers' is an anagram of 'MARKET RESEARCH'.
Can you help me to learn more?
(Other definitions for market research that I've seen before include "Consumer studies" , "test of customers' requirements" , "retail study" , "Study of consumers' needs and preference" , "study of consumer needs" .)