This is speculation, but it does have a ring of authenticity.
The NAPLES-FOGGIA CAMPAIGN was fought on Italian soil, 9 Sept 43 - 21 Jan 44, which would fit the period of Clifford's death, and represents our initial incursion into mainland Italy.
US/British troops landed in Italy 8 Sept 43, with Mark Clark's Fifth Army, 36th Infantry Division, going ashore at Salerno, with45th ID in a "floating reserve".
36th ID and 45th ID were elements of VI Corps at that time. I note the 191st TANK BN wasassigned briefly to 36th ID, but in Aug-44, not Sep-43.
As for the immediate operations on 28 Sept 43, my reference map shows that the US line of attack extended from just below Termoli on the Adreatic Sea in the east, to just below Naples on the Tyrrhenian Sea in the west.
So, one would assume that he was wounded and captured below that line. I am sorry that he died from his wounds.
The US action was spearheaded by US II Corps, which I would assume included the 191st TK BN, among other elements.
Our forces were opposed by 15th Panzer Division, Hermann Goring Panzer Division and 26 Panzer Division, among others.
I will still try to ID the unit/s the 191st TK BN was assigned to prior to 28 Sept 43. Without charge. OK ?
The cemetery he is buried in is just out of Anzio. I have visited it several times over the years. It is a beautiful setting.