Observe the French ship at all events (10)
I believe the answer is:
regardless
'at all events' is the definition.
(thesaurus)
'observe the french ship' is the wordplay.
'observe' becomes 'regard' (I've seen this before).
'the french' becomes 'le' ('the' in French).
'ship' becomes 'ss'.
'regard'+'le'+'ss'='REGARDLESS'
(Other definitions for regardless that I've seen before include "Without heed" , "Lacking consideration" , "in spite of everything" , "Indifferent - come what may" , "Heeding no one - one of the 14 films" .)