Pat is anxious on starting school (6)
I believe the answer is:
caress
'pat' is the definition.
(I know that pat is a more specific form of the action caress)
'anxious on starting school' is the wordplay.
'anxious' becomes 'cares' (I can't explain this - if you can you should believe this answer much more).
'on' indicates putting letters inside (as in clothing 'on' a person).
'starting' says to take the initial letters.
The initial letter of 'school' is 's'.
'cares' enclosing 's' is 'CARESS'.
'is' is the link.
Can you help me to learn more?
(Other definitions for caress that I've seen before include "pet" , "Stoke affectionately" , "Stroke lovingly" , "Touch with affection" , "Stroke fondly" .)