A Roman's terribly small joint shows ability to row (11)
I believe the answer is:
oarsmanship
'ability to row' is the definition.
I can't tell whether this definition defines the answer.
'a roman's terribly small joint' is the wordplay.
'terribly' is an anagram indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'joint' becomes 'hip joint' (part of body).
'a'+'romans'='aromans'
'aromans' is an anagram of 'oarsman'.
'oarsman'+'s'+'hip'='OARSMANSHIP'
'shows' acts as a link.
Can you help me to learn more?
(Other definitions for oarsmanship that I've seen before include "Rowing skill" , "crafty skill" , "Rowers provide" .)