Don't go to bed son - do these exercises (6)
I believe the answer is:
situps
'these exercises' is the definition.
(I've seen this before)
'don't go to bed son' is the wordplay.
'don't go to bed' becomes 'sit up' (to sit up is to stay up late).
'son' becomes 's' (genealogical abbreviation for son).
'situp'+'s'='SITUPS'
'do' is the link.
This may not be right. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for situps that I've seen before include "Physical training exercises" , "Gym exercises" , "Exercises for the stomach" , "Forms of physical exercise" .)