Words with "a" in the first part:
* Giveaway: (give + away)
* Graveyard: (grave + yard)
* Gameplay: (game + play)
* Graybeard: (gray + beard)
* Gateway: (gate + way)
* Grassland: (grass + land)
Words with "a" in the second part:
* Breakaway: (break + away)
* Comeback: (come + back)
* Checkmate: (check + mate)
* Wasteland: (waste + land)
* Heartbreak: (heart + break)
* Haystack: (hay + stack)
Words with "a" in both parts:
* Playmate: (play + mate)
* Haymaker: (hay + maker)
* Daybreak: (day + break)
* Hairspray: (hair + spray)
* Stairway: (stair + way)
This is not an exhaustive list, but it should give you a good starting point!