Associated with altered appearance (7)
I believe the answer is:
Here is my best explanation:
'associated' is the definition.
(relating is a kind of associating)
'altered appearance' is the subsidiary indication.
'altered' anagrams to 'related'.
However, I am not sure how the anagram is indicated.
'with' is the link.
(Other definitions for related that I've seen before include "were sympathetic", "Members of the same family must be", "As siblings obviously are", "Kindred", "Of the same family", "Linked", "Told (a story etc)", "Connected - told", "Told in detail, being connected" and "Treadle (anag) - akin".)