Clarke hopes issues over Sessegnon's paperwork can be resolved in time for next week's clash with Sunderland.
"When you transfer from one club to another you have to reapply for your work permit," said the Albion boss, who is optimistic Shane Long's knee injury is not too serious.
"There was a little glitch in the process yesterday that delayed it and unfortunately for us he wasn't available.
"Hopefully it will be resolved over the weekend, or Monday at the latest, and he'll be available to face his old club next Saturday."
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