Clue: Row in boxing arena because of matches where severe blow is likely (7,7)
Answer: ROARING FORTIES
Explanation: Definition: where severe blow is likely
 OAR(to row with, well, oars) **contained in**(in) RING(boxing arena – a square ring) + FOR(because of, as in "he failed for lack of experience") + TIES(sporting matches between two sides).
Defn: The ocean tracts between latitudes 40 and 50 degrees south which experience very severe winds/blows.