A case that may be looked into (5)
I believe the answer is:
Here is my best explanation:
'a case' is the definition.
'may be looked into' is the wordplay.
I cannot quite understand how this works, but
'be' could be 'rate' (rating is a kind of being) and 'rate' is found within the answer.
A single letter 'c' remains which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'that' is the link.
(Other definitions for crate that I've seen before include "Jalopy", "Wooden case", "Carton; old plane", "Container", "old car", "Packing case with wooden slats", "Old soldiers might be found in this", "Packing-case made of wooden slats", "Box for shipping" and "Old car".)