Fearless Latvian on manoeuvres (7)
I believe the answer is:
valiant
'fearless' is the definition.
(similar in meaning)
'latvian on manoeuvres' is the wordplay.
'on manoeuvres' indicates an anagram (the letters manoeuvre into a new form).
'latvian' anagrammed gives 'VALIANT'.
(Other definitions for valiant that I've seen before include "Courageous, determined" , "Latvian (anag.)" , "Showing courage" , "Heroic" , "Doughty" .)