One who may outdo another in trivial parts (5)
I believe the answer is:
rival
'one who may outdo another in trivial parts' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'one who may outdo another' is the wordplay.
I cannot really see how this works, but
'one' could be 'i' (Roman numeral) and 'i' is found within the answer.
'another' could be 'r' (I've seen this in other clues) and 'r' is found within the answer.
The remaining letters 'val' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for rival that I've seen before include "Be equal to in quality" , "Compete with" , "Adversary, antagonist" , "Contender" , "Adversary or foe" .)