Page, back to front — the cause of head-scratching for setter? (4)
I believe the answer is:
pets
'setter?' is the definition.
(I know that setter is a type of hunting dog)
'page back to front the cause of head-scratching' is the wordplay.
'page' becomes 'p'.
'back to' says to take the final letters.
'cause' indicates an anagram.
'of head' says to take the initial letters (I've seen 'head' mean this).
The final letters of 'front the' are 'te'.
The initial letter of 'scratching' is 's'.
'te' anagrammed gives 'et'.
'p'+'et'+'s'='PETS'
'for' is the link.
(Other definitions for pets that I've seen before include "Domestic animals" , "Little darlings - step on them" , "Domesticated animals" , "Animals at home" .)