Relating to, characteristic of, or befitting a clerk; scholarly, literate, or organized in manner.
From 'clerk' plus the adjectival suffix '-ly' (which forms adjectives from nouns, as in kingly, queenly, or ghostly).
Interestingly, '-ly' can form both adjectives (scholarly, ghostly) and adverbs (quickly, slowly), which sometimes confuses learners—'clerkly' as an adjective means like a clerk, while 'clerkly' as an adverb (rarely used) would mean in a clerk-like manner.
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