Teases learner on requirement to test within (7)
I believe the answer is:
needles
'teases' is the definition.
(I've seen this in another clue)
'learner on requirement to test within' is the wordplay.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'on' means one lot of letters go next to another.
'requirement' becomes 'need' (synonyms).
'to test within' becomes 'es' (I can't explain this - if you can you should believe this answer much more).
'l' put after 'need' is 'needl'.
'needl'+'es'='NEEDLES'
Can you help me to learn more?
(Other definitions for needles that I've seen before include "Isle of Wight feature - irritates" , "Annoys, pointers" , "landmark" , "Heckles" , "Is annoying" .)