Complete space with flag (6)
I believe the answer is:
entire
'complete' is the definition.
(synonyms)
'space with flag' is the wordplay.
'space' becomes 'en' (in printing, a space as wide as a letter 'n').
'with' is a charade indicator (letters next to each other).
'flag' becomes 'tire' (both can mean to become weary).
'en'+'tire'='ENTIRE'
(Other definitions for entire that I've seen before include "Whole; absolute" , "With no part left out" , "excluding nothing" , "everything" , "Full, intact" .)