Clan Guildmage
Creature — Human Shaman
, 
: Target creature can't block this turn.
, : Target land you control becomes a 4/4 Elemental creature with haste until end of turn. It's still a land.
Tomasz Jedruszek
Ravnica Allegiance (RNA)
• #162Rulings
Clan Guildmage’s second ability doesn’t untap the land that becomes a creature.
(wotc • 2019-01-25)
Activating Clan Guildmage’s first ability after a creature has blocked won’t remove the blocking creature from combat or cause the creature it blocked to become unblocked.
(wotc • 2019-01-25)
Rulings
Clan Guildmage’s second ability doesn’t untap the land that becomes a creature.
(wotc • 2019-01-25)
Activating Clan Guildmage’s first ability after a creature has blocked won’t remove the blocking creature from combat or cause the creature it blocked to become unblocked.
(wotc • 2019-01-25)