Our group at university tracks shark's activity (5)
I believe the answer is:
usury
'shark's activity' is the definition.
(as in a loan shark - usury is unethical lending)
'our group at university tracks' is the wordplay.
'our group' becomes 'us'.
'at' is a charade indicator (letters next to each other).
'university' becomes 'u' (abbreviation for university).
'tracks' becomes 'RY' (abbreviation for railway).
'us'+'u'+'ry'='USURY'
(Other definitions for usury that I've seen before include "Lending money at excessive rates of interest" , "Demanding excessive interest" , "Extortionate moneylending" , "Lending at high interest rates" , "Lending of money at exorbitant interest" .)