Pig-headed botanist stupidly taking an E (9)
I believe the answer is:
obstinate
'pig-headed' is the definition.
(I've seen this before)
'botanist stupidly taking an e' is the wordplay.
'stupidly' indicates anagramming the letters (a stupid ordering of the letters).
'taking' means one lot of letters go next to another.
'botanist' anagrammed gives 'obstinat'.
'obstinat'+'e'='OBSTINATE'
(Other definitions for obstinate that I've seen before include "Like mules" , "Cussed" , "Blindly stubborn" , "Stubborn, obdurate" , "Stubborn or unyielding" .)