A helpful shipping line? (7)
I believe the answer is:
towrope
'a helpful shipping line?' is the definition.
'towrope' can be an answer for 'line?' (towrope is a kind of line). I am unsure of the 'a helpful shipping' bit.
'shipping line?' is the wordplay.
'shipping' becomes 'tow' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'line?' becomes 'rope' (line can mean a piece of rope).
'tow'+'rope'='TOWROPE'
Can you help me to learn more?
(Other definitions for towrope that I've seen before include "AA might assist with this" , "Cable for hauling vehicle or vessel" , "Cable used after breakdowns" , "What may pull broken-down vehicle" , "Pulling cable" .)