Pulls small locomotives (7)
I believe the answer is:
strains
'pulls' is the definition.
The answer and definition can be both acts as well as being plural nouns.
Maybe there's a link between them I don't understand?
'small locomotives' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'locomotives' becomes 'trains'.
's'+'trains'='STRAINS'
Can you help me to learn more?
(Other definitions for strains that I've seen before include "Tries very hard" , "Melodies" , "Stresses and - -" .)