Marks made by small creatures (5)
I believe the answer is:
ticks
'creatures' is the definition.
(tick is a kind of creature)
'marks made by small' is the wordplay.
I cannot really understand how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is located in the answer.
The remaining letters 'tick' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for ticks that I've seen before include "Marks correct" , "covers" , "They suck from warm-blooded animals" , "Parasitic mites" , "Parasitic insects" .)