Pampers sailor that is aboard British ship at first (6)
I believe the answer is:
babies
'pampers' is the definition.
('baby' can be a synonym of 'pamper')
'sailor that is aboard british ship at first' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'aboard' means one lot of letters goes inside another.
'at first' indicates taking the first letters.
The first letters of 'british ship' is 'bs'.
'ab'+'ie'='abie'
'abie' inserted inside 'bs' is 'BABIES'.
(Other definitions for babies that I've seen before include "Small children" , "Infants" , "Storks' freight?" , "Recently born children" , "Very young children" .)