He shows dad a clever wheeze (7)
I believe the answer is:
patrick
'he' is the definition.
'dad a clever wheeze' is the wordplay.
'dad' becomes 'pa' (synonyms).
'a clever wheeze' becomes 'trick' (I am not sure about this - if you are sure you should believe this answer much more).
'pa'+'trick'='PATRICK'
'shows' acts as a link.
Can you help me to learn more?
(Other definitions for patrick that I've seen before include "Ireland's patron saint" , "Irish patron saint" , "- - Swayze: film actor" , "-- Moore, astronomer" , "Patron saint who said 'Shoo!' to serpents" .)