Data's vague on rambling being beneficial (12)
I believe the answer is:
advantageous
'beneficial' is the definition.
('advantageous' can be similar in meaning to 'beneficial')
'data's vague on rambling' is the wordplay.
'rambling' is an anagram indicator.
'datas'+'vague'+'on'='datasvagueon'
'datasvagueon' is an anagram of 'ADVANTAGEOUS'.
'being' is the link.
(Other definitions for advantageous that I've seen before include "Profitable" , "Useful, beneficial" , "Favourable" .)