I'm grateful for that piebald hack (3,4)
I believe the answer is:
tap into
'hack' is the definition.
I know nothing about this answer so I cannot judge whether this works.
'i'm grateful for that piebald' is the wordplay.
'i'm grateful' becomes 'ta' (both can mean thank you).
'for' means one lot of letters go next to another.
'that piebald' becomes 'pinto' (I've seen this before).
'ta'+'pinto'='TAP INTO'
Can you help me to learn more?
(Other definitions for tap into that I've seen before include "gain illegal access" , "Secretly gain access to" .)