He had a key qualification in the premiership (5)
I believe the answer is:
major
'key qualification in the premiership' is the definition.
'major' can be an answer for 'key' (thesaurus). I am not sure about the 'qualification in the premiership' bit.
'he had a' is the wordplay.
I cannot quite see how this works, but
'he' could be 'jo' and 'jo' is found in the answer.
'a' is within the answer.
The remaining letters 'mr' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for major that I've seen before include "1 down's predecessor" , "Military rank" , "Of greater importance or stature" , "grave" , "John --, prime minister" .)