A five letter work for a fire starter could be match.
Begin is a good start!
arson
Stoke
Inferno
A 5 letter word starting with you is young or youth.
after
'swarm' is a 5 letter word and begins with SW.
A 5-letter word for an intense fire is a blaze.
earlyeliteenjoyenterexits
appleabaftabashabbeyabideabateaboutaboveabyssacornadmitadoptadultadoreadornaffixafireafootafteragainagileagreeaheadalderalertalien
after
ashes
amity
hello hover
wooer
abase