Covertly
looking at someone secretly with out then knowing or a noob
told secretly
The word for looking at someone or something secretly is "spying" or "peeking".
Beware!
fob
The word you are looking for is "conspire". It means to plan something secretly with others.
No secretly s an adverb, secret can be an adjective eg She has a secret friend
Guard is another word for look out. Additional synonyms include shotgun, protect and watch.
infatuated?
Secretly is an adverb. It modifies verbs by providing information on how an action is performed.
watch, observe, see