Answer: spyon

AnswerCrossword Clue
SPYON

Track, as the feds might do to a suspect

SPYON

Watch secretly

SPYON

Watch covertly

SPYON
Secretly watch
SPYON
Watch, secret agent-style
SPYONWatch from the trees, say
SPYONWatch surreptitiously
SPYONWatch from hiding
SPYONObserve through a keyhole
SPYONWatch through a keyhole
SPYONObserve surreptitiously
SPYONFollow
SPYONKeep under surveillance
SPYONInvestigate, perhaps
SPYONObserve covertly
SPYONSurveil
SPYONBug
SPYONWatch furtively
SPYONWatch in secret
SPYONTail, perhaps
SPYONSecretly observe
SPYONTail, maybe
SPYONWatch secretly.
SPYONObserve furtively
SPYONWatch slyly
SPYONWatch through binoculars, say
SPYONObserve secretly
SPYONShadow, e.g.
SPYONView slyly
SPYONBug, say