Warning by hotel; root vegetable in India’s not good, about to return (9)
I believe the answer is:
harbinger
'warning' is the definition.
(I've seen this before)
'hotel root vegetable in india's not good about to return' is the wordplay.
I cannot really see how this works, but
'hotel' could be 'h' (phonetic alphabet: alpha, bravo, charlie etc.) and 'h' is located in the answer.
'in' is within the answer.
'good' could be 'g' (abbreviation) and 'g' is present in the answer.
'about' could be 'a' (abbreviation in Chambers) and 'a' is found in the answer.
This may be the basis of clue (or it may be nonsense).
'by' acts as a link.
Can you help me to learn more?
(Other definitions for harbinger that I've seen before include "omen" , "sign of things to come" , "Early sign" , "One announcing approach" , "It indicates the future" .)