straighten out is a verb meaning "settle or put right". It carries 6 recorded senses.
change for the better
“The lazy student promised to reform”
“the habitual cheater finally saw the light”
make straight
make free from confusion or ambiguity; make clear
“Could you clarify these remarks?”
“Clear up the question of who is at fault”
put (things or places) in order
“Tidy up your room!”
Definitions, synonyms and semantic relations for straighten out come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.