Learner he met outside in biker's lid (6)
I believe the answer is:
helmet
'lid' is the definition.
(helmet is a kind of lid)
'learner he met outside' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'outside' means one lot of letters goes inside another.
'he'+'met'='hemet'
'l' inserted inside 'hemet' is 'HELMET'.
'in biker's' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for helmet that I've seen before include "Tin hat" , "Safety hat" , "Protective casing for the head" , "to provide capital protection" , "Protection for top" .)