Fix power supply in that broadcast (6)
I believe the answer is:
attach
'fix' is the definition.
(I know that fix is a more specific form of the action attach)
'power supply in that broadcast' is the wordplay.
'power supply' becomes 'ac' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'in' is an insertion indicator.
'broadcast' indicates anagramming the letters (letters scattered or cast around).
'that' is an anagram of 'atth'.
'ac' inserted into 'atth' is 'ATTACH'.
Can you help me to learn more?
(Other definitions for attach that I've seen before include "Conjoin, affix" , "Join, connect" , "'Affix, fasten (6)'" , "Fasten - attribute" , "Bind, fasten" .)