Comes close to Spithead? (5)
I believe the answer is:
nears
'comes' is the definition.
(nearing is a kind of coming)
'close to spithead?' is the wordplay.
'close to' becomes 'near' (I've seen this before).
'spithead?' becomes 's' (head letter of 'spit').
'near'+'s'='NEARS'
(Other definitions for nears that I've seen before include "Draws close" , "Moves closer to" , "Becomes closer" , "Draws closer to" , "Uses snare to get closer" .)