Row over Atlantic, losing very badly (11)
I believe the answer is:
altercation
'row' is the definition.
(altercation is a kind of row)
'over atlantic losing very badly' is the wordplay.
'losing' suggests deleting specific letters.
'very' becomes 'v' (abbreviation).
'badly' indicates anagramming the letters.
'over'+'atlantic'='overatlantic'
'overatlantic' with 'v' taken out is 'oeratlantic'.
'oeratlantic' anagrammed gives 'ALTERCATION'.
(Other definitions for altercation that I've seen before include "heated dispute" , "breeze" , "Noisy quarrel" , "heated argument" , "Noisy disagreement" .)