Good person having to dress flasher at disco (6)
I believe the answer is:
'flasher at disco' is the definition.
'good person having to dress' is the wordplay.
'good person' becomes 'st' (saint).
'having' says to put letters next to each other.
'to dress' becomes 'robe' (robing is a kind of dressing).
(Other definitions for strobe that I've seen before include "Protestant reformer" , "Sorbet (anag) -flashing light" , "Sister to Hansel" , "Sort of lighting" , "Rapidly flashing lighting often used on stage" .)