One cardinal crossing river shows some guts (9)
I believe the answer is:
intestine
'some guts' is the definition.
(I've seen this before)
'one cardinal crossing river shows' is the wordplay.
'one' becomes 'i' (Roman numeral).
'cardinal' becomes 'nine' (a cardinal number).
'crossing' is an insertion indicator (to cross can mean to go over or around).
'river shows' becomes 'test' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'nine' enclosing 'test' is 'ntestine'.
'i'+'ntestine'='INTESTINE'
Can you help me to learn more?
(Other definitions for intestine that I've seen before include "Part of the alimentary canal" , "Some guts" , "canal section" , "Being gutted, one loses it" .)