Possible to spend clue tokens to re-roll attempts at sealing gates?
You can spend clue tokens to roll extra dice for any skill check, including closing gates.  You can spend them one at a time, and stop after you have a success.

After you've successfully closed the gate you can then spend five clue tokens to seal it (assuming you still have that many).

Rerolls are different, generally given by skills and items.  With a reroll you reroll all dice in the pool, including any added by clue tokens that you have spent.