Be in veil, disguised? Good thinking (9)

I believe the answer is:

believing

'thinking' is the definition.
('believe' can be a synonym of 'think')

'be in veil disguised? good' is the wordplay.
'disguised?' indicates anagramming the letters.
'good' becomes 'g' (abbreviation).
'in'+'veil'='inveil'
'inveil' is an anagram of 'lievin'.
'be'+'lievin'+'g'='BELIEVING'

(Another definition for believing that I've seen is " Crediting".)

I've seen this clue in The Telegraph.

Want a hint initially instead of a full solution? Install my app