Some characters with influence are slim (4)

I believe the answer is:

thin

'slim' is the definition.
(I know that slim can be written as thin)

'some characters with influence are' is the wordplay.
'some characters' indicates the answer is hidden within the clue (some letters or characters from the clue).
'THIN' is hidden within 'with influence are'.

(Other definitions for thin that I've seen before include "Slender, slight" , "Slim - watery" , "as 7 [LOAF] may be sliced" , "Lean; narrow" , "Flimsy" .)

I've seen this clue in The Irish Times.

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