Answer:
Clean
Step-by-step explanation:
The sentence 'He ran off to pu on a clean shirt' has one adjective, which is the word 'clean' that describes the noun shirt. So, in the sentence, the other words are:
He - personal pronoun
ran off - a phrasal verb : to leave a place or person in a way that people disapprove of.
to - infinitive of purpose
put on - phrasal verb - dress oneself.