Healthy tips by one in DNA unit producing cleanliness (7)
I believe the answer is:
hygiene
'cleanliness' is the definition.
(I've seen this in another clue)
'healthy tips by one in dna unit' is the wordplay.
'tips' says to hollow out the word (remove centre letters) (just the outer letters of the world).
'by' is a charade indicator (letters next to each other).
'one' becomes 'i' (Roman numeral).
'in' means one lot of letters goes inside another.
'dna unit' becomes 'gene' (I've seen this before).
'healthy' with its middle taken out is 'hy'.
'i' inserted inside 'gene' is 'giene'.
'hy'+'giene'='HYGIENE'
'producing' acts as a link.
(Other definitions for hygiene that I've seen before include "Clean and healthy practices" , "Clean, healthy habits" , "The practice or conditions of cleanliness" , "Practice of cleanliness to maintain health" , "Condition promoting sanitary practices" .)