Soldier on exercises eyes invader (5,3,3)

I believe the answer is:

never say die

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'soldier on exercises eyes invader' is the definition.
I can't judge whether this defines the answer.

'exercises eyes invader' is the wordplay.
'exercises' indicates an anagram (letters exercise or move around).
'eyes'+'invader'='eyesinvader'
'eyesinvader' anagrammed gives 'NEVER-SAY-DIE'.

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(Other definitions for never say die that I've seen before include "Don't stop" , "Persevere!" , "Be resolute" , "don't give up hope" , "Refuse to give up" .)

I've seen this clue in The Times.

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