chemical defence vs British spelling

chemical defence and British spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemical defence	Yes	No	No	No
British spelling	Yes	No	No	No

chemical defence (noun)	British spelling (noun)
procedures involved in taking defensive measures against attacks using chemical agents	English orthography used in the UK, Ireland and most of the Commonwealth (characterized by 'analyse', 'centre' and 'useable')