A foot farther back (3)
I believe the answer is:
aft
'back' is the definition.
(associated in meaning)
'a foot farther' is the wordplay.
'foot farther' becomes 'ft' (synonyms. I am not sure about the 'farther' bit.).
'a'+'ft'='AFT'
Can you help me to learn more?
(Other definitions for aft that I've seen before include "At the back at sea" , "Toward's a ship's stern" , "Of ship, fat in the rear" , "At the back of a ship" , "Towards rear (of ship)" .)