Tree’s height: in two minds about it (5)
I believe the answer is:
thorn
'tree's' is the definition.
(thorn can mean a hawthorn)
'height in two minds about it' is the wordplay.
'height' becomes 'h' (abbreviation in geometry).
'in two minds' becomes 'torn' (both can mean indecisive).
'about it' means one lot of letters goes inside another (some letters go around or about others).
'h' put into 'torn' is 'THORN'.
(Other definitions for thorn that I've seen before include "Source of irritation" , "Feature of rose tree" , "(Rose's) prickle" , "Invariable accompaniment of 2, they say" , "eg Prickle on rose" .)