wingman

Short definition from Wiktionary

Noun

1. 1
   A pilot partner of another; a pilot who flies in the same wing or squadron.
2. 2
   A friend who accompanies one to offer (or receive) support, especially in flirting with love interests.
3. 3
   A player positioned on the wing.

Verb

1. 1
   To act as a wingman for (someone); to accompany in order to provide support.