Trifle cheers date (3)
I believe the answer is:
tad
'trifle' is the definition.
(I've seen this in another clue)
'cheers date' is the wordplay.
'cheers' becomes 'ta' (both can mean thank you).
'date' becomes 'd' (abbreviation e.g. dob - date of birth).
'ta'+'d'='TAD'
(Other definitions for tad that I've seen before include "little boy" , "Modest amount" , "A small amount (colloq.)" , "(A) bit, touch" , "Smidgen" .)