Surprise birthday parties often involve them (5)
I believe the answer is:
ruses
'surprise birthday parties often involve them' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ruses that I've seen before include "Clever stratagems" , "Cunning plans" , "'Stratagems, tricks (5)'" , "Dodges" , "Tricks or deceptions" .)