Tree expert's data on each trunk is on time (11)
I believe the answer is:
genealogist
'tree expert's' is the definition.
(expert in family trees)
'data on each trunk is on time' is the wordplay.
I cannot really understand how this works, but
'data' could be 'gen' (I've seen this in other clues) and 'gen' is found within the answer.
'each' could be 'ea' (abbreviation) and 'ea' is found within the answer.
'is' is within the answer.
'time' could be 't' (abbreviation) and 't' is located in the answer.
The remaining letters 'log' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for genealogist that I've seen before include "Student of descent" , "who may explore a particular line" , "Ancestor tracer" .)