Intending flu treatment to be significant (10)
I believe the answer is:
meaningful
'significant' is the definition.
(similar in meaning)
'intending flu treatment' is the wordplay.
'intending' becomes 'meaning' ('mean' can be a synonym of 'intend').
'treatment' indicates an anagram (letters treated or processed differently).
'flu' anagrammed gives 'ful'.
'meaning'+'ful'='MEANINGFUL'
'to be' acts as a link.
(Other definitions for meaningful that I've seen before include "Important" , "Significant" .)