Kind of pop record's sleeve showing lack of harmony (7)
I believe the answer is:
discord
'lack of harmony' is the definition.
(I've seen this before)
'kind of pop record's sleeve' is the wordplay.
'kind of pop' becomes 'disco' (disco music).
'sleeve' says to hollow out the word (remove centre letters) (I've seen 'sleeves' mean this (sleeve can mean the outside letters)).
'record' with its middle removed is 'rd'.
'disco'+'rd'='DISCORD'
'showing' acts as a link.
(Other definitions for discord that I've seen before include "Opposition" , "Friction" , "Lack of agreement" , "Disagreement" , "Strife, lack of harmony" .)