Thanks Redroger.
Sort of what I am guessing at. Have come across 'carrier' in respect of mail when googling.
Definitely 'Carryer' in 3 baptism records. And his grandson had what appears to be big business between Lincoln and London - with his great grandson eventually rising to Commissary-General. So there is family interest in transport of goods possibly starting with John - perhaps even earlier. John's son and grandson both became Mayors of Lincoln, so at a guess John had some standing in the local community.
The early 1700s must have been 'exciting' time to be in transport business - one would guess difficult and dangerous.
Other relatives, in another separate branch are agricultural and coincidentally recorded in the censuses as 'carter's. I can see that as a farming trade.
However the precise description of John as a 'Carryer' suggests a bit more than a man with a cart.
Trying to guess at its significance 300 years on is probably fruitless.
My message here is in hope of discovering someone with in-depth knowledge of that time, or perhaps who has come across a description of 'carryer' as a trade in the early eighteenth century.
In my imagination a 'carryer' could be transporting goods, people, and/or mail - probably all three. To do so would require horses and all their requirements, staging posts, associates and partners.