Skirt that essentially limits riding (4)
I believe the answer is:
midi
'skirt' is the definition.
(I've seen this in another clue)
'essentially limits riding' is the wordplay.
'essentially' indicates the central letters.
'riding' becomes 'di' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The central letters of 'limits' are 'mi'.
'mi'+'di'='MIDI'
'that' is the link.
Can you help me to learn more?
(Other definitions for midi that I've seen before include "Medium-sized" , "Cover reaching calves" , "Le ..., the south of France" , "Calf-length skirt" , "Female attire" .)