Left a little chap out, having slipped (4)
I believe the answer is:
slid
'slipped' is the definition.
('slide' can be a synonym of 'slip')
'left a little chap out' is the wordplay.
'left' becomes 'l' (common abbreviation).
'a little chap' becomes 'sid' (I am not sure about the 'little' bit.).
'out' indicates putting letters inside.
'l' placed into 'sid' is 'SLID'.
'having' is the link.
Can you help me to learn more?
(Other definitions for slid that I've seen before include "Slipped" , "Moved (eg, on ice)" , "Moved smoothly along a surface" , "Skidded, slewed" .)