League leaders prolonged their outstanding victory sequence with a dominant three-one scoreline against a player-down their opponents.
Frank Lampard's squad got off to a ideal start with Brandon Thomas-Asante and Jamie Allen scoring the back of the net within the first seven minutes.
Tatsuhiro Sakamoto added a three-goal advantage just before the interval, while a Watford defender was dismissed before the break.
The midfielder converted a spot-kick for the away squad, but it was nothing more than a late goal.
The home side's shot-stopper the keeper had before saved a clear opportunity for Watford, which could have altered the contest early on.
Lampard commented: âThat was a tough fixture today because the opposition are a good side.â
The substitute was introduced from the substitutes to net the lone goal in a 1-0 win over the Baggies.
Ipswich dominated the play but only broke the deadlock near the end thanks to Clarke's fifth goal of the season.
Ryan Mason's side thought they had scored in stoppage time, but the effort was chalked off for a offense in the area.
Hayden Matthews headed a late own goal to present Mark Robins' team a narrow win.
The home side have at present won just one game since the close of last month.
Robins commented: âIt was among the most important victories weâve had this season.â