See us having yen to be very bad (5)
I believe the answer is:
lousy
'be very bad' is the definition.
(I've seen this before)
'see us having yen' is the wordplay.
'see' becomes 'lo' (archaic word meaning 'look!').
'having' says to put letters next to each other.
'yen' becomes 'y'.
'lo'+'us'+'y'='LOUSY'
'to' is the link.
(Other definitions for lousy that I've seen before include "Very poor (colloq.)" , "Infested: mean" , "Very poor or bad" , "Second-rate" , "Awful" .)