Tracheophyte plant grown at last by retired judge (4)
I believe the answer is:
fern
'tracheophyte plant' is the definition.
(I've seen this before)
'grown at last by retired judge' is the wordplay.
'at last' suggests the final letters.
'by' says to put letters next to each other.
'retired' shows that the letters should be reversed in order.
'judge' becomes 'ref'.
The last letter of 'grown' is 'n'.
'ref' reversed gives 'fer'.
'n' put after 'fer' is 'FERN'.
(Other definitions for fern that I've seen before include "Type of plant" , "Non-flowering plant" , "Flowerless plant with feathery fronds" , "Tracheophyte plant" , "Often shady plant" .)