Parts of document getting left out -- the reasons? (6)

I believe the answer is:

causes

I'm a little stuck... Click here to teach me more about this clue!

'the reasons?' is the definition.

I don't understand the remainder of the clue.

(Other definitions for causes that I've seen before include "They produce effects" , "Origins or crusaders" , "Gives rise to -- crusades" , "Brings" , "They give rise to effects" .)

I've seen this clue in The Telegraph.

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