Black on black on black is traditional for covert ops:
And as Beverly and Worf wear the same outfit as Jean-Luc, we can assume it is Starfleet issue spy wear.
As seen on Section 31, Starfleet’s spy division:
In the first cap the extra on the left is wearing what Jean-Luc wears in “Chain of Command” while Leland has the same uniform as the operatives in Enterprise.
This ridging isn’t evident in the other caps, only in this last scene when he’s been captured and will be stripped, which leads me to believe it’s worn under the black top. Presumably as a thermal layer, possibly a kind of armor.
For the infiltration scene, he also wears a tunic in what appears to be velour or similar. Based on the olive-brown color and v-neck style (both traits of Jean-Luc’s personal aesthetic as seen in his Casual Wear) I think it’s either something he chose himself or something he actually owns.