She means a lot to dad (3)
I believe the answer is:
pam
'she' is the definition.
'a lot to dad' is the wordplay.
'a lot' becomes 'm'.
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'dad' becomes 'pa' (both can mean one's father).
'm' after 'pa' is 'PAM'.
'means' acts as a link.
(Other definitions for pam that I've seen before include "Female" , "- Ayres, English poet" , "Short girl's name" .)