Plant's lock-up bolt (5)
I believe the answer is:
lupin
'plant's' is the definition.
The answer is an example.
'lock-up bolt' is the wordplay.
I cannot quite see how this works, but
'up' is present in the answer.
The remaining letters 'lin' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for lupin that I've seen before include "Garden plant of the pea family" , "Spiked flower" , "Plant with flowers on long spikes" , "Flower with spike of usually purplish-blue flowers" , "Flower called after wolf" .)