Cares halved at first? Can't decide (2,3,5)
I believe the answer is:
in two minds
'can't decide' is the definition.
(someone who can't decide is in two minds)
'cares halved at first?' is the wordplay.
'cares' becomes 'minds'.
'halved' becomes 'intwo' (something halved is split in two).
'at first?' is a charade indicator (letters next to each other).
'minds' after 'intwo' is 'IN TWO MINDS'.
(Other definitions for in two minds that I've seen before include "Torn" , "where similar ideas may be foolish or clever" , "The outcome is uncertain" , "Wavering, undecided" , "like Dr Jekyll at times?" .)