Motorway tracks around London area, causing intense unhappiness (6)
I believe the answer is:
misery
'intense unhappiness' is the definition.
(I've seen this before)
'motorway tracks around london area' is the wordplay.
'motorway' becomes 'mi' (resembles M1, English motorway).
'tracks' becomes 'ry'.
'around' means one lot of letters goes inside another.
'london area' becomes 'se' (abbreviation for South East).
'mi'+'ry'='miry'
'miry' enclosing 'se' is 'MISERY'.
'causing' is the link.
(Other definitions for misery that I've seen before include "Great suffering" , "Wretchedness, suffering" , "Great distress or discomfort" , "Woe, wretchedness" , "Intense unhappiness" .)