Where one might look up who, having directed, failed to impress (12)
I believe the answer is:
underwhelmed
'might look up who having directed failed to impress' is the definition.
The definition suggests a past participle verb which matches the answer.
'where one' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'where' is 'erwhe' which is present in the answer.
'one' could be 'un' (northern English dialect form of 'one') and 'un' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for underwhelmed that I've seen before include "Less than impressed" , "Far from pleased or stirred" .)