Available for one wrongly parted by force (2,5)
I believe the answer is:
on offer
'available' is the definition.
(eg available for sale)
'for one wrongly parted by force' is the wordplay.
'wrongly' is an anagram indicator.
'parted by' is an insertion indicator.
'force' becomes 'F' (symbol used in Physics e.g. f=ma).
'for'+'one'='forone'
'forone' with letters rearranged gives 'onofer'.
'onofer' enclosing 'f' is 'ON OFFER'.
(Other definitions for on offer that I've seen before include "At special price" , "available for less" , "is made cheaper?" , "For sale at specified price" , "For sale at a certain price" .)