agenda
to be on the agenda

be on
to be on to a good thing

beam-ends
to be on her beam-ends

behaviour
to be on one's best behaviour

booze
to be on the booze

breadline
to be on the breadline

brink
to be on the brink of...

cusp
to be on the cusp of

defensive
to be on the defensive

downer
to be on a downer

fatigue
to be on fatigue

handshaking
to be on handshaking terms with a person

knife-edge
to be on a knife-edge

lone
...to be on one's lone / to

lookout
to be on the lookout

lurk
to be on the lurk

mending
to be on the mending hand

mooch
to be on the mooch

newspaper
to be on a newspaper

periphery
to be on the periphery of...

piecework
to be on piecework

rampage
to be on the rampage

tapis
to be on the tapis

tightrope
...to be on a tightrope / to walk on a tightrope

uptrend
to be on uptrend

ventilator
to be on a ventilator

wallaby
to be on the wallaby (track)

wane
to be on the wane

warpath
to be on the warpath

wavelength
to be on the same wavelength