Crewing a Vehicle requires tapping creatures you control with total power meeting or exceeding the Vehicle's crew number (CR 702.122b). Nothing in the crew mechanic restricts which creatures can be used — only that they are untapped and that their combined power is sufficient.
Defender (CR 702.3a) states only that the creature "can't attack." It places no restriction on tapping the creature for costs or activated abilities. Tapping to crew is simply paying a cost, not attacking.
Because the two abilities are completely independent, a creature with defender is a perfectly legal crew participant. Its inability to attack is irrelevant to the crew action.
Example: You control a Wall of Omens (0/4, defender). You also control Smuggler's Copter (Crew 1). You tap Wall of Omens (power 0... wait — Crew 1 requires power ≥ 1). Actually, Wall of Omens has power 0, so it alone can't crew Smuggler's Copter; you'd need a defender with power ≥ 1, like Lagonna-Band Elder (3/4, defender). Tap it to crew Smuggler's Copter — completely legal despite defender.
In short: defender restricts only the attack step (CR 702.3a, 508.1a), never the tapping of a creature for costs. Any untapped creature with sufficient power can crew a Vehicle regardless of defender.
Unofficial fan resource — not affiliated with or endorsed by Wizards of the Coast. Answers are AI-generated estimates grounded in the Comprehensive Rules and are not a substitute for an official judge. Verify anything match-critical.