The leaders of D-class, E-class and Mersey including Tamar, ultimately are excellent (5)
I believe the answer is:
dream
'the leaders' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'd-class e-class and mersey including tamar ultimately are excellent' is the wordplay.
I cannot quite see how this works, but
'd' is present in the answer.
'class' could be 're' (Religious Education, school subject) and 're' is found within the answer.
'are' could be 'a' (short for 'are', historical unit of measurement) and 'a' is present in the answer.
A single letter 'm' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for dream that I've seen before include "Switch off" , "Trance" , "Part of sleep" , "Perfect" , "Reverie or nightmare" .)