That is breaking metal connection (3-2)
I believe the answer is:
tie-in
'connection' is the definition.
(I've seen this before)
'that is breaking metal' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'breaking' means one lot of letters goes inside another.
'metal' becomes 'tin' (tin is a kind of metal).
'ie' put into 'tin' is 'TIE-IN'.
(Other definitions for tie-in that I've seen before include "Coordinate" , "Item linked with popular film, programme etc" , "Related item" , "Agree with" , "Book linked to TV or film production" .)