Did grasp instrument with less concentration! (7)
I believe the answer is:
diluted
'did grasp instrument with less concentration' is the definition.
I can't judge whether this defines the answer.
'did grasp instrument' is the wordplay.
'grasp' means one lot of letters goes inside another.
'instrument' becomes 'lute' (lute is a kind of instrument).
'did' enclosing 'lute' is 'DILUTED'.
Can you help me to learn more?
(Other definitions for diluted that I've seen before include "reduced in strength" , "Weaker" , "Lessened the strength of a solution" , "Watered down or attenuated." .)