Slow pitch received glowing coverage (6)
I believe the answer is:
retard
'slow' is the definition.
(I know that slow can be written as retard)
'pitch received glowing coverage' is the wordplay.
'pitch' becomes 'tar' (synonyms).
'received glowing' becomes 'red' (red hot. I am not sure about the 'received' bit.).
'coverage' means one lot of letters goes inside another.
'tar' placed within 'red' is 'RETARD'.
Can you help me to learn more?
(Other definitions for retard that I've seen before include "Hinder progress" , "Delay effect of" , "Check" , "Slow down growth" , "Hold back, slow progress" .)