It's clever to call round at the back (6)
I believe the answer is:
crafty
'it's clever' is the definition.
(I've seen this in another clue)
'call round at the back' is the wordplay.
'call' becomes 'cry' (as in a bird's call).
'round' means one lot of letters goes inside another.
'at the back' becomes 'aft' (aft means towards or at the end of a ship).
'cry' placed around 'aft' is 'CRAFTY'.
'to' is the link.
(Other definitions for crafty that I've seen before include "Cunning - shrewd" , "Devious" , "Cunning and artful" , "'Cunning, wily (6)'" , "Cunning, deceitful" .)