Turner's affair, heading off to Spain (5)
I believe the answer is:
hinge
'turner's' is the definition.
(a hinge turns or swings)
'affair heading off to spain' is the wordplay.
'affair' becomes 'thing' (synonyms).
'heading off' means to remove the first letter.
'to' says to put letters next to each other.
'spain' becomes 'e' (abbreviation for Espana).
'thing' with its first letter removed is 'hing'.
'hing'+'e'='HINGE'
(Other definitions for hinge that I've seen before include "Joint between door and frame" , "Flexible joint" , "On what a door swings" , "Door support" , "Moveable joint" .)