A number of those caught up in Puritan ethics (3)
I believe the answer is:
ten
'a number of' is the definition.
'up in puritan ethics' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in' indicates the answer is hidden within the clue.
'net' can be found hidden inside 'puritan ethics'.
'net' in reverse letter order is 'TEN'.
'those caught' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for ten that I've seen before include "X-WORD" , "time" , "honour" , "PM's address, Downing St" , "No of sides of a decagon" .)