Seventy - stripped for the occasion! (5)
I believe the answer is:
event
'the occasion' is the definition.
(I've seen this before)
'seventy stripped' is the wordplay.
'stripped' indicates the central letters (outside letters removed).
The central letters of 'seventy' are 'EVENT'.
'for' is the link.
(Other definitions for event that I've seen before include "Incident, occurrence" , "Thing that happens" , "Occurence, occasion" , "Happening, noteworthy perhaps" , "special occasion" .)