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 informally mean thank you).
'date' becomes 'd' (common abbreviation eg in 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" .)