Explore (6)
'explore' is the definition.
(I know that explore can be written as search)
This is the entire clue.
(Other definitions for search that I've seen before include "Examine (to find something)" , "Try to find something by looking" , "Pursue a chaser" , "Explore" , "Look for something or someone, perhaps chaser" .)
(Other definitions for sightsee that I've seen before include "What a tourist does with vision" , "visit the Lions?" , "Visit places of interest" , "Visit interesting places" , "take in views" .)