Beginning to strip, strip off frock (8)
I believe the answer is:
sundress
'frock' is the definition.
(I've seen this before)
'beginning to strip strip off' is the wordplay.
'beginning to' suggests taking the first letters.
'strip off' becomes 'undress' (I've seen this before).
The initial letter of 'strip' is 's'.
's'+'undress'='SUNDRESS'
(Other definitions for sundress that I've seen before include "evident when the heat is on" , "Summer frock" .)