Liam regularly studies poorly, showing apathy (9)
I believe the answer is:
lassitude
'apathy' is the definition.
(lassitude is a kind of apathy)
'liam regularly studies poorly' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
'poorly' indicates anagramming the letters (a poor spelling).
The alternating letters of 'liam' are 'la'.
'studies' with letters rearranged gives 'ssitude'.
'la'+'ssitude'='LASSITUDE'
'showing' acts as a link.
(Other definitions for lassitude that I've seen before include "Listlessness, lethargy" , "Lack of energy and enthusiasm" , "30 [LETHARGY]" , "Listlessness, fatigue" , "Weariness" .)