Appointment to meet son, tense after test (5)
I believe the answer is:
tryst
'appointment' is the definition.
(tryst is a kind of appointment)
'meet son tense after test' is the wordplay.
'meet' says to put letters next to each other.
'son' becomes 's'.
'tense' becomes 't' (abbreviation used in many dictionaries).
'after' is a charade indicator (letters next to each other).
'test' becomes 'try' ('try' can be a synonym of 'test').
's'+'t' is 'st'.
'st' after 'try' is 'TRYST'.
'to' is the link.
(Other definitions for tryst that I've seen before include "Date" , "(Secret) meeting between lovers" , "Secret assignation" , "Romantic meeting" , "cattle-fair" .)