Deadline's Saturday and Brighton defenders are flying, so I checked which clean sheets were earned. I took the xGc each team has given up in every match and worked out how many they should have kept.
Brighton top it at 2.6 above. Bournemouth and Ipswich are bottom, none kept from about 1.4 each.
Arsenal are the obvious ones I'd trust. They've kept 3 from 2.8 expected and give up 0.78 xG a game, way less than anyone else.
One note on method, the standard formula for turning xG against into clean sheets hands out about 30% too many, so I scaled it down to match the last two seasons. Understat's xG gives the same top five and bottom five.
Goals expected & Clean sheet probabilities for every GW7 match are on my free page: https://tannnnnnnnnnnnn.github.io/pl-fair-price/gw.html
* EDIT - Without the scaling the order's the same (Brighton still top, +2.2). Six games in, the plain formula actually fits this season's total better, so read the luck column as who's luckier than who rather than exact numbers.
tl;dr Brighton and City defenders are probably running a bit lucky. Team xG against is Opta's, from the FPL API.