This is the 516th most frequent Chinese word.
守
To guard; to defend; to observe; to abide by.
Here, '守' is used to mean 'abide by' or 'adhere to', in this case, adhering to being on time.
我们要守时，不要迟到。
We should be punctual and not be late.
In this context, '守' indicates 'to keep' as in keeping one’s word or commitment.
他承诺要守信，不会欺骗别人。
He promised to keep his word and not deceive others.
'守' refers to guarding or protecting a place, expressing the action of being protective.