Join in broad daylight (3)
I believe the answer is:
add
'join' is the definition.
(thesaurus)
'in broad daylight' is the wordplay.
'in' indicates the answer is hidden within the clue.
'ADD' is hidden within 'broad daylight'.
(Other definitions for add that I've seen before include "Reason for difficulty learning" , "problem for hyperactive children" , "Count up" , "put two and two together" , "Sum, total" .)