Builds prisoner's trust moving around cell, primarily (10)
I believe the answer is:
constructs
'builds' is the definition.
('construct' can be a synonym of 'build')
'prisoner's trust moving around cell primarily' is the wordplay.
'prisoner's' becomes 'cons' (abbreviation for 'convict').
'moving' indicates an anagram (letters are moved around).
'around' means one lot of letters goes inside another.
'primarily' suggests taking the first letters.
The initial letter of 'cell' is 'c'.
'trust' with letters rearranged gives 'truts'.
'truts' going around 'c' is 'tructs'.
'cons'+'tructs'='CONSTRUCTS'
(Another definition for constructs that I've seen is " Makes".)