Do as pigs crossing dale regularly (7)
I believe the answer is:
swindle
'do' is the definition.
(I've seen this before)
'pigs crossing dale regularly' is the wordplay.
'pigs' becomes 'swine' (I've seen this before).
'crossing' means one lot of letters goes inside another.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternate letters of 'dale' are 'dl'.
'swine' going around 'dl' is 'SWINDLE'.
'as' acts as a link.
(Other definitions for swindle that I've seen before include "skin" , "Diddle, sting, twist" , "fleece" , "Scam" , "Cheat; fraud" .)