Parents touring an isthmus? (6)
I believe the answer is:
panama
'isthmus?' is the definition.
(I've seen this in another clue)
'parents touring an' is the wordplay.
'parents' becomes 'pama' (Pa and Ma).
'touring' indicates putting letters inside (touring can mean going round).
'pama' enclosing 'an' is 'PANAMA'.
(Other definitions for panama that I've seen before include "Wide-brimmed hat" , "Hat; Central Am. canal" , "Canal zone" , "Criticise" , "Hat woven from jipijapa leaves" .)