Kind nurse, extremely lonely (8)
I believe the answer is:
sisterly
'kind' is the definition.
(thesaurus)
'nurse extremely lonely' is the wordplay.
'nurse' becomes 'sister' (I've seen this before**).
'extremely' suggests removing the centre.
'lonely' with its centre taken out is 'ly'.
'sister'+'ly'='SISTERLY'
(Other definitions for sisterly that I've seen before include "relatively close" , "Friendly in a female way" , "I try less (anag.)" , "Like a female relative" , "Reportedly none" .)