Beautiful lass taking drug to party (4,4)
I believe the answer is:
fine gael
'party' is the definition.
(Irish political party)
'beautiful lass taking drug' is the wordplay.
I cannot quite understand how this works, but
'beautiful' could be 'fine' (similar in meaning) and 'fine' is found within the answer.
'drug' could be 'e' (E is another name for ecstasy) and 'e' is present in the answer.
'lass' could be 'gal' (I've seen this before) and 'gal' is located in the remaining letters.
This accounts for all the letters.
This explanation may well be incorrect...
'to' is the link.
(Other definitions for fine gael that I've seen before include "Irish political party" , "party in Ireland" , "The main opposition political party" , "Political party in 1 across" .)