Arrived a few moments ago with patient, as a precaution (4,2,4)
I believe the answer is:
just in case
'as a precaution' is the definition.
(I've seen this before)
'arrived a few moments ago with patient' is the wordplay.
I cannot quite see how this works, but
'arrived' could be 'in' (I've seen this in other clues) and 'in' is located in the answer.
'a' is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for just in case that I've seen before include "In the unlikely event of problems" , "how one should be when judging suit?" , "For insurance" , "Lest" , "as a precaution" .)