Answer: weaklink

AnswerCrossword Clue
WEAKLINKChain concern
WEAKLINKVulnerable part, as of a chain
WEAKLINKVulnerable spot in a chain
WEAKLINKChain breaker, so to speak
WEAKLINKUndependable group member
WEAKLINKLikely cause of system failure
WEAKLINKAchilles' heel.