Marks made by bolts (5)
I believe the answer is:
'marks' is the definition.
The answer and definition can be both acts as well as being plural nouns.
Perhaps they are linked in a way I don't understand?
'made by bolts' is the wordplay.
'made by' indicates anagramming the letters (another word made by the same letters).
'bolts' with letters rearranged gives 'BLOTS'.
Can you help me to learn more?
(Another definition for blots that I've seen is " Stains, perhaps on copybook".)