Six bringing skill to practicality (9)
I believe the answer is:
viability
'to practicality' is the definition.
(viability is a kind of practicality)
'six bringing skill' is the wordplay.
'six' becomes 'VI' (Roman numerals).
'bringing' means one lot of letters go next to another.
'skill' becomes 'ability' (I've seen this in another clue).
'vi'+'ability'='VIABILITY'
(Other definitions for viability that I've seen before include "likelihood of success" , "Aptitude for living" .)