First to board popular ship refuses to take no for an answer (7)
I believe the answer is:
insists
'refuses to take no for an answer' is the definition.
I can't tell whether this definition defines the answer.
'first to board popular ship' is the wordplay.
'first to' becomes 'ist' (I've seen this in other clues).
'board' is an insertion indicator.
'popular' becomes 'in' ('in' can mean trendy).
'ship' becomes 'SS' (prefix in ship names eg SS Great Britain).
'in'+'ss'='inss'
'ist' put into 'inss' is 'INSISTS'.
Can you help me to learn more?
(Other definitions for insists that I've seen before include "Demands firmly, not accepting refusal" , "Brooks no refusal" , "Contends" , "Maintains persistently" , "Maintains firmly" .)