Mark, irritating little thing (4)

I believe the answer is:

tick

I believe this clue is a double definition.

'mark' is the first definition.
(I know that tick is a type of mark)

'irritating little thing' is the second definition.
(irritating parasite)

(Other definitions for tick that I've seen before include "Small parasitic arachnid" , "Credit (sl.)" , "Clock's sound" , "Mark of work done (right)" , "Credit (slang)" .)

I've seen this clue in The Telegraph.

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