Holds back when crossing black spot (8)
I believe the answer is:
abstains
'holds back' is the definition.
The definition and answer can be both to do with social activities as well as being verbs in their -s form.
Maybe there's a link between them I don't understand?
'when crossing black spot' is the wordplay.
'when' becomes 'as'.
'crossing' means one lot of letters goes inside another.
'black' becomes 'b' (as in pencil classifications).
'spot' becomes 'stain' ('stain' can be a synonym of 'spot'**).
'b'+'stain'='bstain'
'as' enclosing 'bstain' is 'ABSTAINS'.
Can you help me to learn more?
(Other definitions for abstains that I've seen before include "Chooses not to do" , "Declines to vote" , "Avoids" , "'doesn't drink'" , "Refrains" .)