When unsure, it is better to leave the doubtful part out than to guess.
Tips
usage
Read 阙 in the old written sense of a gap or missing part, where it stands in for 缺 (lacking). The set phrase 阙疑 means to leave a doubtful point open rather than fill it with a guess.
The gate radical, wrapping the character. It fits because 阙 are the watchtowers that flank a palace gate, the structure standing guard at the entrance.
phonetic
欮jué
to dig out; to exhaust
Sits inside the gate and supplies the sound (jué shifting to què). It also lends a faint sense of a gap or hollow, matching the 'deficiency' meaning.