Surround the foreign boat at the bottom of lock (7)
I believe the answer is:
ringlet
'lock' is the definition.
(both can mean a piece of someone's hair)
'surround the foreign boat at the bottom' is the wordplay.
'surround' becomes 'ring' (synonyms).
'the foreign' becomes 'le' ('the' in French).
'at the bottom' indicates one should take the final letters.
The last letter of 'boat' is 't'.
'ring'+'le'+'t'='RINGLET'
'of' acts as a link.
(Other definitions for ringlet that I've seen before include "A curl - kind of tingler" , "Curling lock of hair" , "Hair feature" , "Bit of hair" , "Cluster of hair" .)