Instrument for which there was a clear call (7)
I believe the answer is:
clarion
This might be a double definition.
'instrument for which there was a clear' is the first definition.
'clarion' can be an answer for 'instrument' (clarion is a kind of instrument). I'm unsure of the rest of the definition.
'call' is the second definition.
(I've seen this before)
Can you help me to learn more?
(Other definitions for clarion that I've seen before include "A loud rousing sound" , "Clear and ringing" , "Loud and clear; shrill war trumpet" , "It makes a shrill note" , "In church maybe stop" .)