Watch old boy attend to customers (7)
I believe the answer is:
observe
'watch old' is the definition.
'observe' can be an answer for 'watch' (observing is a kind of watching). I'm not certain of the 'old' bit.
'attend to customers' is the wordplay.
'attend' becomes 'serve' (synonyms).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'customers' becomes 'ob' (I am not sure about this - if you are sure you should believe this answer much more).
'serve' put after 'ob' is 'OBSERVE'.
'boy' acts as a link.
Can you help me to learn more?
(Other definitions for observe that I've seen before include "Notice, watch" , "Watch attentively" , "Espy" , "See - keep - remark - maintain - celebrate" , "Discern" .)