see the explanation below.
maybe you mean an infinitive phrase that functions as an adjective.
Let’s define the concepts first.
Adjectives are words describing an idea.
Infinitive is a kind of verbal or fake verb having the formula to + base form of the verb.
Examples:to walk to talk to run to plan to encode to watch to dance to play
Infinitive phrase is a phrase composed of infinitive and the words/ ideas following it.
to eat right to solve the difficult equation to speak in English
In the second example to solve is the infinitive and the difficult equation is the additional idea.
When we say adjective infinitive phrase it is an infinitive phrase that describes a noun or the idea that comes first before it.
##1.##The instructions to follow right away is very unclear.
to follow right away is the adjective infinitive phrase and the instruction is the noun being describe.
##2.## The place to visit amazingly is Paris.
to visit amazingly is the adjective infinitive phrase and the place is the noun being describe.
Hope this helps.