Explosive alert in court battle (8)
I believe the answer is:
waterloo
'battle' is the definition.
(1815 battle)
'explosive alert in court' is the wordplay.
'explosive' indicates an anagram.
'in' indicates putting letters inside.
'court' becomes 'woo' (both can mean to romance someone).
'alert' anagrammed gives 'aterl'.
'aterl' placed into 'woo' is 'WATERLOO'.
(Other definitions for waterloo that I've seen before include "6D 5A [TUBE STATION]" , "Battle; Abba hit" , "Where Napoleon Bonaparte lost it" , "Historic battle" , "Total or crushing defeat" .)