On that account, see alone (4)
I believe the answer is:
solo
'alone' is the definition.
(as in a musical solo)
'on that account see' is the wordplay.
'on that account' becomes 'so' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'see' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'so'+'lo'='SOLO'
Can you help me to learn more?
(Other definitions for solo that I've seen before include "On one's own, unaccompanied" , "Lone" , "Han - (Star Wars); fly unaccompanied" , "Performance by one person" , "Game for four" .)