Mad gambol round university brings pain (7)
I believe the answer is:
lumbago
'pain' is the definition.
(I know that lumbago is a type of backache)
'mad gambol round university' is the wordplay.
'mad' indicates an anagram.
'round' indicates putting letters inside.
'university' becomes 'U' (abbreviation for university).
'gambol' anagrammed gives 'lmbago'.
'lmbago' going around 'u' is 'LUMBAGO'.
'brings' is the link.
(Other definitions for lumbago that I've seen before include "Back problem" , "Gaul mob (anag.)" , "Lower back ache" , "Rheumatic backache" , "Maul bog badly for a rheumatic affliction" .)