Heard fight had two aspects (4)
I believe the answer is:
dual
'had two aspects' is the definition.
The answer and definition are not the same part of speech. However, past participle verbs and adjectives can occasionally define each other.
'heard fight' is the wordplay.
'heard' indicates a 'sounds like' (homophone) clue.
'fight' becomes 'duel' (dueling is a kind of fighting).
'duel' sounds like 'DUAL'.
Can you help me to learn more?
(Other definitions for dual that I've seen before include "Road with central division" , "Double" , "Having two distinct functions" , "Consisting of pairs" , "Twofold" .)