Oddly, dress Penny with possibly crude sack (7)
I believe the answer is:
despoil
'sack' is the definition.
(I've seen this before)
'oddly dress penny with possibly crude' is the wordplay.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'penny' becomes 'p'.
'with' means one lot of letters go next to another.
'possibly crude' becomes 'oil' (crude oil is a type of oil).
The alternating letters of 'dress' are 'des'.
'des'+'p'+'oil'='DESPOIL'
(Other definitions for despoil that I've seen before include "Plunder - I sloped (anag)" , "Plunder completely" , "Steal from (a place)" , "Ravage" , "Plunder (a place)" .)