Monument captain's installed on pitch (9)
I believe the answer is:
headstone
'monument' is the definition.
(headstone is a kind of monument)
'captain's installed on pitch' is the wordplay.
'captain's installed' becomes 'heads' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' means one lot of letters go next to another.
'pitch' becomes 'tone' (tone is a kind of pitch).
'heads'+'tone'='HEADSTONE'
Can you help me to learn more?
(Other definitions for headstone that I've seen before include "Its stands over a grave, duly inscribed" , "Grave marker" , "Slab set at the head of a grave" , "Memorial on a grave" , "It is set up on a grave with inscriptions" .)