Im pretty sure. Otherwise, it would just say you need an additional clue, without specifying 'connected town' (not gate). Needing 6 clues instead of 5 is harder already, just not as hard as if they were of the same colour!
Assuming you typed the card text exactly correct (I don't have the card in from of me right now) I would think that it is referring to the town that the gate is connected to, not another town that the town is connected to.
It's a lot harder to get 6 cards of one colour than to get one additional card of another colour.
The intended official ruling is that you need 5 cards of one color as per normal + 1 additional card of a different color, with the different color being one of the two towns that is connected to the town's gate you are trying to close. So, for example, if you had Yig out and were trying to close Arkham, you would need 5 green Arkham cards + 1 card from either Innsmouth (purple) or Dunwich (yellow), whichever you choose.
So does that mean the investigator needs 4 cards of the same color and one extra of the connecting town because thats what happened to me on the final gate. Depending which way this goes means i either won the game or lost it.