As well as the normal external interrupts INT0 and INT1 you can also wake the chip through a variety of other interrupts. One of those is the pin change interrupt.
In the datasheet is a table of what is available in the different sleep modes, and what can wake you from that sleep mode. I have compressed the table to remove a lot of the stuff you don't care about at the moment and just show the "wake-up sources":
As you can see both INT and PCINT can wake from all modes (along with TWI [Wire.h] slave mode address matching).
The note (3) on the table just says that for INT0 and INT1 it must be a LOW level interrupt, not a RISING or FALLING. No mention is made of the type of interrupt for PCINT.
So yes, since pin 7 has PCINT facilities (all pins on the ATMega328P have PCINT) you can configure that as a wake-up source and wake the MCU using pin 7.