Did include stringed instrument which made it less intense (7)
I believe the answer is:
diluted
'made it less intense' is the definition.
I can't tell whether this definition defines the answer.
'did include stringed instrument' is the wordplay.
'include' is an insertion indicator.
'stringed instrument' becomes 'lute' (lute is a type of stringed instrument).
'did' enclosing 'lute' is 'DILUTED'.
'which' acts as a link.
Can you help me to learn more?
(Other definitions for diluted that I've seen before include "Weaker" , "reduced in strength" , "Watered down or attenuated." , "Lessened the strength of a solution" .)