Boatman, at heart European, in first part of Tory attack (4,4)
'attack' is the definition.
(I've seen this before)
'boatman at heart european in first part of tory' is the wordplay.
'boatman' becomes 'tar' (tar is an informal term for a sailor).
'at' becomes 'in'.
'heart european' becomes 'e' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' is an insertion indicator.
'first part of' indicates taking half (the first half of the word).
'tarin' placed around 'e' is 'tearin'.
'tory' cut in half is 'to'.
(Other definitions for tear into that I've seen before include "handbag", "Attack verbally", "Scold furiously".)