The majority are about half dead and not particularly good (6)
I believe the answer is:
modest
'and not particularly good' is the definition.
I can't tell whether this defines the answer.
'the majority are about half dead' is the wordplay.
'the majority' becomes 'most' (most of a group).
'are about' means one lot of letters goes inside another.
'half' suggests halving the letters.
'dead' with half the letters taken is 'de'.
'most' going around 'de' is 'MODEST'.
Can you help me to learn more?
(Other definitions for modest that I've seen before include "Reserved" , "Decorous" , "Demure" , "Prudent" , "Not vain or showy" .)