Subsequently catching hot fever (6)
I believe the answer is:
lather
'fever' is the definition.
(as in getting yourself into a fever or lather)
'subsequently catching hot' is the wordplay.
'subsequently' becomes 'later' (subsequently means later on).
'catching' indicates putting letters inside.
'hot' becomes 'h' (abbreviation, eg on taps).
'later' going around 'h' is 'LATHER'.
(Other definitions for lather that I've seen before include "Whip up froth - tizzy" , "Soapsuds" , "Foamy soap as for shaving" , "Froth, thrash (colloq.)" , "Agitated state" .)