The sentence reads:
... thorough preparation and daily practice will be essential.
In British/International English, would the word used here be "practice" or "practise"?
I understand the distinction between the noun vs verb spelling, I am just unsure as to whether practice/practise is functioning as a noun or verb in this case.
In American English "Practise" and "Practice" are just alternative forms of themselves, because they both perform the function of verb and noun. In British English, the difference is made by being "Practice" a noun and "Practise" a verb.
The practice (noun) is used in a sentence as an "action" that is already being performed. The practise (verb) is used in the sentence as an "action" to be performed, like something what was done, or has to be performed in the future.
The above is not a strict rule but it can help to differentiate its use quickly.
In British English, the spelling follows the rule of advice:advise::noun:verb.
If the intended meaning of the two-word phrase in your title was to describe a regular activity done on a daily basis, then the word 'daily' would be an adjective and 'practice' would be a noun.
If the phrase was intended as an injunction or command, then the word 'practise' would be a verb and 'daily' would be an adverb.
The word order (as well as the spelling) would usually distinguish the two meanings.
