Journey making half of capital laugh madly? (4,4)
I believe the answer is:
long haul
'journey' is the definition.
(long haul is a kind of journey)
'half of capital laugh madly?' is the wordplay.
'half of capital' becomes 'lon' (half of 'London').
'madly?' is an anagram indicator (I've seen 'madly' mean this).
'laugh' anagrammed gives 'ghaul'.
'lon'+'ghaul'='LONG-HAUL'
'making' is the link.
(Other definitions for long haul that I've seen before include "Protracted process, effort" , "Journey over a great distance" , "Journey (or enterprise) that will take time" , "prolonged effort" , "Hard and lengthy task" .)