People after area in abandoned section of plant (4,5)
I believe the answer is:
leaf trace
'section of plant' is the definition.
'people after area in abandoned' is the wordplay.
'people' becomes 'race' (people can mean a national group or race).
'after' says to put letters next to each other.
'area' becomes 'a' (maths abbreviation).
'in' means one lot of letters goes inside another.
'abandoned' becomes 'left' (I've seen this before).
'a' inserted into 'left' is 'leaft'.
'race' after 'leaft' is 'LEAF TRACE'.
(Another definition for leaf trace that I've seen is " Part of plant".)