Tolerant to allow nine to get changed inside (7)
I believe the answer is:
lenient
'tolerant' is the definition.
(similar in meaning)
'allow nine to get changed inside' is the wordplay.
'allow' becomes 'let' (synonyms).
'to get changed' is an anagram indicator (letters change around).
'inside' indicates putting letters inside.
'nine' with letters rearranged gives 'nien'.
'let' going around 'nien' is 'LENIENT'.
'to' is the link.
(Other definitions for lenient that I've seen before include "Forgiving, gentle" , "Forgiving, soft" , "Indulgent, lax" , "Light" , "'Indulgent, easy (7)'" .)