Noun clause refers to the group of words acting as a noun. They do not form a complete sentence, in other words, these are dependent clauses.
A noun clause can act as an object of preposition also. A preposition is included in a noun clause in order to give further details.
Therefore, the sentence in which the underlined clause is a noun clause that functions as the object of a preposition is:
Veteran trainers offer a great deal of love and discipline to (whatever dogs they train.)
wherein 'to' is the preposition modifying the noun clause "whatever dogs they train."