It is Muhammad, captain in sloping style (7)
I believe the answer is:
italics
'it is muhammad captain' is the definition.
The definition suggests a singular noun but the answer is a plural noun.
'sloping style' is the wordplay.
'sloping' becomes 'italic' (I've seen this before).
'style' becomes 's' (this might be a standard abbreviation I've not previously seen).
'italic'+'s'='ITALICS'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for italics that I've seen before include "Letters slanting upward to the right" , "List CIA with letters that slant" , "They emphasise" , "Letters in sloping type" , "way of writing?" .)