Detective on instrument having diminished concentration (6)
I believe the answer is:
dilute
'diminished concentration' is the definition.
The answer and definition are different parts of speech. However, past participle verbs and adjectives occasionally define each other.
'detective on instrument' is the wordplay.
'detective' becomes 'di' (Detective Inspector abbreviation).
'on' says to put letters next to each other.
'instrument' becomes 'lute' (lute is a kind of instrument).
'di'+'lute'='DILUTE'
'having' acts as a link.
Can you help me to learn more?
(Other definitions for dilute that I've seen before include "Lessen the strength of a solution" , "Tone down" , "Reduce in strength or concentration" , "Reduce concentration of a liquid" , "Add water to thin" .)