Stop Henry coming to the worst conclusion (4)
I believe the answer is:
halt
'stop' is the definition.
(halting is a kind of stopping)
'henry coming to the worst conclusion' is the wordplay.
'henry' becomes 'hal'.
'coming to' is a charade indicator (letters next to each other).
'conclusion' says to take the final letters.
The last letter of 'worst' is 't'.
'hal'+'t'='HALT'
(Other definitions for halt that I've seen before include "Limp; minor station" , "Small railway station" , "Stop; minor station" , "Stop, small station" , "Stop or pause" .)