'Tigers', men trained for army units (9)
I believe the answer is:
regiments
'army units' is the definition.
(regiment is a kind of army unit)
'tigers men trained' is the wordplay.
'trained' indicates an anagram (to train can mean to grow something into a shape).
'tigers'+'men'='tigersmen'
'tigersmen' with letters rearranged gives 'REGIMENTS'.
'for' acts as a link.
(Other definitions for regiments that I've seen before include "fighting units" , "Organises" , "groups of soldiers" .)