Try, seeing enemies losing heart, perhaps (5)
I believe the answer is:
essay
'try' is the definition.
('essay' can be a synonym of 'try')
'enemies losing heart perhaps' is the wordplay.
'losing heart' says to hollow out the word (remove centre letters).
'perhaps' becomes 'say'.
'enemies' with its centre removed is 'es'.
'es'+'say'='ESSAY'
'seeing' acts as a link.
(Other definitions for essay that I've seen before include "Short literary piece: attempt" , "What may be written in exam" , "Trial, piece of writing" , "Try; dissertation" , "Composition, paper, article" .)