Sympathy strike at harbour (7)
I believe the answer is:
rapport
'sympathy' is the definition.
(rapport is a kind of sympathy)
'strike at harbour' is the wordplay.
'strike' becomes 'rap' (synonyms).
'at' says to put letters next to each other.
'harbour' becomes 'port' (I've seen this before).
'rap'+'port'='RAPPORT'
(Other definitions for rapport that I've seen before include "Sympathetic understanding" , "Feeling of mutual understanding" , "Harmonious and understanding relationship between people" , "Sympathetic relationship" , "Mutual harmony and affinity" .)