Clear it is off the rails and down to earth (9)
I believe the answer is:
realistic
'rails and down to earth' is the definition.
I can't tell whether this definition defines the answer.
'clear it is off' is the wordplay.
'off' is an anagram indicator.
'clear'+'it'+'is'='clearitis'
'clearitis' anagrammed gives 'REALISTIC'.
'the' is the link.
Can you help me to learn more?
(Other definitions for realistic that I've seen before include "Faithful" , "Lifelike" , "Practical; true to life" , "accurate picture" , "Without illusions, dealing in facts" .)