Should have got them off first, I reckoned (9)
I believe the answer is:
methought
'should have got them' is the definition.
I can't tell whether this defines the answer.
'first i reckoned' is the wordplay.
'first' says to put letters next to each other.
'i' becomes 'me'.
'reckoned' becomes 'thought' ('think' can be a synonym of 'reckon').
'me' next to 'thought' is 'METHOUGHT'.
'off' is the link.
Can you help me to learn more?
(Other definitions for methought that I've seen before include "The speaker concluded" , "I had the impression" , "In old-fashioned way, I considered" .)