Briefly express view about end of tractor plant (5)
I believe the answer is:
orpin
'plant' is the definition.
(orpin is a kind of plant)
'briefly express view about end of tractor' is the wordplay.
'briefly' means to remove the last letter.
'express view' becomes 'opine'.
'about' indicates putting letters inside.
'end of' suggests the final letters.
The last letter of 'tractor' is 'r'.
'opine' with its last letter taken off is 'opin'.
'opin' enclosing 'r' is 'ORPIN'.
(Other definitions for orpin that I've seen before include "Plant" , "Stonecrop that's purple" , "Variety of stonecrop" , "Bloomer" , "Purple, broad-leafed stonecrop" .)