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' is an anagram indicator (a poor spelling).
The alternate letters of 'liam' are 'la'.
'studies' anagrammed gives 'ssitude'.
'la'+'ssitude'='LASSITUDE'
'showing' is the link.
(Other definitions for lassitude that I've seen before include "Listlessness, lethargy" , "Lack of energy and enthusiasm" , "30 [LETHARGY]" , "Listlessness, fatigue" , "Weariness" .)