Can we have an article just before a verb?
Short answer: no.

Longer answer: Sometimes verbs in the -ing form are gerunds, which act like nouns. Verbs have noun form counterparts too: My football team sure took a beating.

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we have a treated area


We have a treated area.

'treated' is a non-finite form of the verb 'treat' — a past participle. A participle may be used as an adjective. Here it modifies the noun 'area'.

If there is no finite auxiliary verb to accompany the non-finite form, it is likely to be an adjective or to be part of a non-finite clause.

a treated area— Here 'treated' is an adjective derived from a verb.
The area was treated.— Here 'was treated' is the main verb phrase of the sentence.

A finite verb phrase cannot be preceded by an article.