"Lord Clive" was drydocked at Plymouth in October and resumed patrols in the Channel before she was taken in hand between 5 December 1917 and 6 April 1918 for modifications to mount the spare 18-inch gun from the large light cruiser , although the gun and mount themselves would not be delivered until 7 September. She bombarded the Tirpitz and Aachen Batteries at Ostend, along with three other monitors, which fired fifty rounds between them during the abortive first attempt to block the Bruges–Ostend Canal that led to the naval base at Bruges on the night of 11 April. The ship supported the Inshore Squadron making the landing attempt during the First Ostend Raid on 23 April with about fifty rounds of 12-inch and some 6-inch shells. "Lord Clive" relieved the monitor as guardship at Yarmouth for five weeks while the latter was refitted. She arrived at Portsmouth on 16 August to have her 18-inch gun fitted. The monitor began operational trials with her new gun on 13 October. She fired one round on 14 October at the bridge at Snaeskerke during the morning, but received no spotting. The ship fired another three rounds later in the day but had to cease fire to avoid hitting friendly advancing troops.