Break in/half tame a piebald nag (3,4)
I believe the answer is:
tap into
'break inhalf tame' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'a piebald nag' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'piebald' could be 'pinto' (I've seen this in another clue) and 'pinto' is found in the answer.
A single letter 't' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tap into that I've seen before include "Secretly gain access to" , "gain illegal access" .)