Prudish people principally dress in fine clothes (5)
I believe the answer is:
primp
'dress in fine clothes' is the definition.
'primp' can be an answer for 'dress' (thesaurus). I'm unsure of the 'in fine clothes' bit.
'prudish people principally' is the wordplay.
'prudish' becomes 'prim' (synonyms).
'principally' suggests taking the first letters.
The initial letter of 'people' is 'p'.
'prim'+'p'='PRIMP'
Can you help me to learn more?
(Other definitions for primp that I've seen before include "Make small adjustments to one's appearance" , "Make fussy adjustments to one's appearance" , "Make minor changes to one's appearance" , "Smarten up" , "Tart up" .)