Flood from Training Centre got type of sickness at times (6)
I believe the answer is:
influx
'flood' is the definition.
(I've seen this before)
'training centre got type of sickness at times' is the wordplay.
'centre' means to look at the middle letters.
'got' says to put letters next to each other.
'type of sickness' becomes 'flu' ().
'at' says to put letters next to each other.
'times' becomes 'x' (multiplication sign).
The central letters of 'training' are 'in'.
'in'+'flu'+'x'='INFLUX'
'from' is the link.
(Other definitions for influx that I've seen before include "Act of flowing in" , "Flow of people into a place" , "Large-scale arrival" , "Mass arrival" , "Inward flow" .)